People wave 'Esteladas' (pro-independence Catalan flags) as they gather during a pro-independence demonstration, on September 11, 2017 in Barcelona during the National Day of Catalonia, the "Diada."
Hundreds of thousands of Catalans were expected to rally to demand their region break away from Spain, in a show of strength three weeks ahead of a secession referendum banned by Madrid. The protest coincides with Catalonia's national day, the "Diada," which commemorates the fall of Barcelona in the War of the Spanish Succession in 1714 and the region's subsequent loss of institutions and freedoms.
 / AFP PHOTO / PAU BARRENA        (Photo credit should read PAU BARRENA/AFP/Getty Images)
PHOTO: PAU BARRENA/AFP/AFP/Getty Images
People wave 'Esteladas' (pro-independence Catalan flags) as they gather during a pro-independence demonstration, on September 11, 2017 in Barcelona during the National Day of Catalonia, the "Diada." Hundreds of thousands of Catalans were expected to rally to demand their region break away from Spain, in a show of strength three weeks ahead of a secession referendum banned by Madrid. The protest coincides with Catalonia's national day, the "Diada," which commemorates the fall of Barcelona in the War of the Spanish Succession in 1714 and the region's subsequent loss of institutions and freedoms. / AFP PHOTO / PAU BARRENA (Photo credit should read PAU BARRENA/AFP/Getty Images)
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PHOTO: Andrew Redington/Getty Images North America/Getty Images
AUGUSTA, GA - APRIL 09: Sergio Garcia of Spain celebrates during the Green Jacket ceremony after he won in a playoff during the final round of the 2017 Masters Tournament at Augusta National Golf Club on April 9, 2017 in Augusta, Georgia. (Photo by Andrew Redington/Getty Images)
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Spain's Prime Minister Mariano Rajoy attends a session of the Upper House of Parliament in Madrid on October 27, 2017. Spanish Prime Minister Mariano Rajoy asked the Senate for the go-ahead to depose Catalan leader Carles Puigdemont and his executive in a bid to stop their independence drive. The central government has invoked the never-before-used article 155 of the Constitution, designed to rein in rebel regions, as it seeks to end Catalonia's drive to break from Spain.
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Catalan President Carles Puigdemont speaks during a statement at the Palau Generalitat in Barcelona, Spain, on Wednesday, Oct. 4, 2017. Catalonia's regional president, Carles Puigdemont, is addressing regional lawmakers on Monday to review a referendum won by supporters of independence from Spain on Oct. 1. (Jordi Bedmar/Presidency Press Service, Pool Photo via AP)
PHOTO: Jordi Bedmar/Pool/AP
Catalan President Carles Puigdemont speaks during a statement at the Palau Generalitat in Barcelona, Spain, on Wednesday, Oct. 4, 2017. Catalonia's regional president, Carles Puigdemont, is addressing regional lawmakers on Monday to review a referendum won by supporters of independence from Spain on Oct. 1. (Jordi Bedmar/Presidency Press Service, Pool Photo via AP)
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BARCELONA, SPAIN - SEPTEMBER 28:  Students get caught in an air vent as they gather to demonstrate against the position of the Spanish government to ban the self-determination referendum of Catalonia during a strike by university students on September 28, 2017 in Barcelona, Spain. The Catalan government is keeping with its plan to hold a referendum, due to take place on October 1, which has been deemed illegal by the Spanish government in Madrid.  (Photo by Dan Kitwood/Getty Images)
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BARCELONA, SPAIN - SEPTEMBER 28: Students get caught in an air vent as they gather to demonstrate against the position of the Spanish government to ban the self-determination referendum of Catalonia during a strike by university students on September 28, 2017 in Barcelona, Spain. The Catalan government is keeping with its plan to hold a referendum, due to take place on October 1, which has been deemed illegal by the Spanish government in Madrid. (Photo by Dan Kitwood/Getty Images)
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BARCELONA, SPAIN - SEPTEMBER 30:  Anti-independence demonstrators march in protest against the independence referendum on September 30, 2017 in Barcelona, Spain. The Catalan government is keeping with its plan to hold a referendum, due to take place on October 1, which has been deemed illegal by the Spanish government in Madrid.  (Photo by Chris McGrath/Getty Images)
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BARCELONA, SPAIN - SEPTEMBER 30: Anti-independence demonstrators march in protest against the independence referendum on September 30, 2017 in Barcelona, Spain. The Catalan government is keeping with its plan to hold a referendum, due to take place on October 1, which has been deemed illegal by the Spanish government in Madrid. (Photo by Chris McGrath/Getty Images)
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Spanish National Police clashes with pro-referendum supporters in Barcelona Sunday, Oct. 1 2017. Catalonia's planned referendum on secession is due to be held Sunday by the pro-independence Catalan government but Spain's government calls the vote illegal, since it violates the constitution, and the country's Constitutional Court has ordered it suspended. (AP Photo/Manu Fernandez)
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Spanish National Police clashes with pro-referendum supporters in Barcelona Sunday, Oct. 1 2017. Catalonia's planned referendum on secession is due to be held Sunday by the pro-independence Catalan government but Spain's government calls the vote illegal, since it violates the constitution, and the country's Constitutional Court has ordered it suspended. (AP Photo/Manu Fernandez)
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Anti-independence demonstrators march waving Spanish flags against the referendum downtown Barcelona on September 30. The planned referendum is due to be held Sunday by the pro-independence Catalan government but Spain's government calls the vote illegal, since it violates the constitution, and the country's Constitutional Court has ordered it suspended.
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Story highlights

Spanish court bars Catalan parliament from meeting

Catalan official says move "unusual and extremely serious"

Catalan president expected to declare independence Monday

(CNN) —  

Spain’s highest court has suspended a meeting of Catalonia’s regional parliament planned for Monday in an apparent attempt to prevent Catalan President Carles Puigdemont’s expected declaration of independence.

The Constitutional Court said Thursday it had issued the suspension decision following a request from the Catalan Socialist Party, which opposes secession.

The parliamentary session was to have been Puigdemont’s first opportunity to make a formal declaration of independence under a Catalan referendum law that the Constitutional Court had previously ruled illegal.

00:51 - Source: CNN
Sergio Garcia calls for Spain to 'be more together'
AUGUSTA, GA - APRIL 09:  Sergio Garcia of Spain celebrates during the Green Jacket ceremony after he won in a playoff during the final round of the 2017 Masters Tournament at Augusta National Golf Club on April 9, 2017 in Augusta, Georgia.  (Photo by Andrew Redington/Getty Images)
PHOTO: Andrew Redington/Getty Images North America/Getty Images
AUGUSTA, GA - APRIL 09: Sergio Garcia of Spain celebrates during the Green Jacket ceremony after he won in a playoff during the final round of the 2017 Masters Tournament at Augusta National Golf Club on April 9, 2017 in Augusta, Georgia. (Photo by Andrew Redington/Getty Images)
Now playing
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Spain's Prime Minister Mariano Rajoy attends a session of the Upper House of Parliament in Madrid on October 27, 2017.
Spanish Prime Minister Mariano Rajoy asked the Senate for the go-ahead to depose Catalan leader Carles Puigdemont and his executive in a bid to stop their independence drive. The central government has invoked the never-before-used article 155 of the Constitution, designed to rein in rebel regions, as it seeks to end Catalonia's drive to break from Spain.
PHOTO: OSCAR DEL POZO/AFP/Getty Images
Spain's Prime Minister Mariano Rajoy attends a session of the Upper House of Parliament in Madrid on October 27, 2017. Spanish Prime Minister Mariano Rajoy asked the Senate for the go-ahead to depose Catalan leader Carles Puigdemont and his executive in a bid to stop their independence drive. The central government has invoked the never-before-used article 155 of the Constitution, designed to rein in rebel regions, as it seeks to end Catalonia's drive to break from Spain.
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Puigdemont urges protests
People wave 'Esteladas' (pro-independence Catalan flags) as they gather during a pro-independence demonstration, on September 11, 2017 in Barcelona during the National Day of Catalonia, the "Diada."
Hundreds of thousands of Catalans were expected to rally to demand their region break away from Spain, in a show of strength three weeks ahead of a secession referendum banned by Madrid. The protest coincides with Catalonia's national day, the "Diada," which commemorates the fall of Barcelona in the War of the Spanish Succession in 1714 and the region's subsequent loss of institutions and freedoms.
 / AFP PHOTO / PAU BARRENA        (Photo credit should read PAU BARRENA/AFP/Getty Images)
PHOTO: PAU BARRENA/AFP/AFP/Getty Images
People wave 'Esteladas' (pro-independence Catalan flags) as they gather during a pro-independence demonstration, on September 11, 2017 in Barcelona during the National Day of Catalonia, the "Diada." Hundreds of thousands of Catalans were expected to rally to demand their region break away from Spain, in a show of strength three weeks ahead of a secession referendum banned by Madrid. The protest coincides with Catalonia's national day, the "Diada," which commemorates the fall of Barcelona in the War of the Spanish Succession in 1714 and the region's subsequent loss of institutions and freedoms. / AFP PHOTO / PAU BARRENA (Photo credit should read PAU BARRENA/AFP/Getty Images)
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Catalan President Carles Puigdemont speaks during a statement at the Palau Generalitat in Barcelona, Spain, on Wednesday, Oct. 4, 2017. Catalonia's regional president, Carles Puigdemont, is addressing regional lawmakers on Monday to review a referendum won by supporters of independence from Spain on Oct. 1. (Jordi Bedmar/Presidency Press Service, Pool Photo via AP)
PHOTO: Jordi Bedmar/Pool/AP
Catalan President Carles Puigdemont speaks during a statement at the Palau Generalitat in Barcelona, Spain, on Wednesday, Oct. 4, 2017. Catalonia's regional president, Carles Puigdemont, is addressing regional lawmakers on Monday to review a referendum won by supporters of independence from Spain on Oct. 1. (Jordi Bedmar/Presidency Press Service, Pool Photo via AP)
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PHOTO: Dan Kitwood/Getty Images
BARCELONA, SPAIN - SEPTEMBER 28: Students get caught in an air vent as they gather to demonstrate against the position of the Spanish government to ban the self-determination referendum of Catalonia during a strike by university students on September 28, 2017 in Barcelona, Spain. The Catalan government is keeping with its plan to hold a referendum, due to take place on October 1, which has been deemed illegal by the Spanish government in Madrid. (Photo by Dan Kitwood/Getty Images)
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PHOTO: Chris McGrath/Getty Images
BARCELONA, SPAIN - SEPTEMBER 30: Anti-independence demonstrators march in protest against the independence referendum on September 30, 2017 in Barcelona, Spain. The Catalan government is keeping with its plan to hold a referendum, due to take place on October 1, which has been deemed illegal by the Spanish government in Madrid. (Photo by Chris McGrath/Getty Images)
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PHOTO: Manu Fernandez/AP
Spanish National Police clashes with pro-referendum supporters in Barcelona Sunday, Oct. 1 2017. Catalonia's planned referendum on secession is due to be held Sunday by the pro-independence Catalan government but Spain's government calls the vote illegal, since it violates the constitution, and the country's Constitutional Court has ordered it suspended. (AP Photo/Manu Fernandez)
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“We are considering what to do,” Carme Forcadell, the regional Parliament’s president, told reporters. “I can assure you that we will defend the sovereignty of the Parliament and the freedom of speech, as well as the lawmakers’ right of initiative.”