(CNN)Belarus' political opposition has said three of its leading members have been abducted, and called for their immediate release.
The Belarusian Coordination Council said in a statement Monday that "unknown people in the center of Minsk" had abducted Maria Kolesnikova, a member of the council's executive committee, as well as press secretary Anton Rodnenkov and executive secretary Ivan Kravtsov.
The council, which is led by main Belarusian opposition candidate Svetlana Tikhanovskaya, is a body aimed at coordinating a peaceful and orderly transition of power in the wake of August's disputed elections.
In an interview with Christiane Amanpour on Monday, Tikhanovskaya said she was "sure" that Kolesnikova was kidnapped. Speaking from Vilnius, Lithuania, she said members of the Coordination Council have been "chased, kidnapped and harassed."
"We are sure that (Kolesnikova) was kidnapped in the morning, but what was going on after this, we are not sure, because we still don't have answers," Tikhanovskaya said. "Maybe she fled to a foreign country or maybe she's still in jail. Nobody knows."
Local news website Tut.by reported that Kolesnikova was abducted Monday morning in the capital of Belarus, citing an eyewitness named as "Anastasia."
CNN has been unable to independently verify that the three opposition figures were abducted. A spokesperson for the council earlier told CNN that the organization has been unable to contact any of the trio on their mobile phones.
Belarusian authorities did not respond to CNN's request for comment, and have not commented publicly on the alleged abduction. The council did not respond to CNN's request for information why they believe that Rodnenkov and Kravtsov were abducted.
"At the moment, members of the Coordinated Council I created are chased, kidnapped and harassed. And it's worrying me a lot, because at the moment we still don't know where Maria Kolesnikova is," Tikhanovskaya told CNN.
"We have received information that she went to the Ukraine. We can't confirm this, maybe it's fake news. It's not normal that the body which was created just for organizing dialogue between authorities and the nation is prosecuted."
British Foreign Secretary Dominic Raab also said on Twitter Monday that he was "seriously concerned" for the welfare of Kolesnikova, and called her safe return the "highest priority."
Reports of the alleged kidnappings emerged after a fourth consecutive weekend of anti-government protests in the country. Unrest erupted in Belarus shortly after its August 9 election in which President Alexander Lukashenko claimed a contested victory.
Lukashenko, who has ruled for 26 years and is often described as Europe's last dictator, has remained defiant in the face of the protests.
Tikhanovskaya was the opposition candidate in the vote, which independent observers criticized as neither free nor fair. Tens of thousands of people have marched against the government in Minsk in the wake of the election.
Tikhanovskaya said in a statement released earlier Monday: "The regime is engaged in terror, there is no other name for it. The kidnapping of Maria Kolesnikova, Anton Rodnenkov and Ivan Kravtsov is an attempt to disrupt the work of the Coordination Council. But that won't stop us."
On Sunday the Coordination Council also said that another prominent activist, Olga Kolvakova was blindfolded, put into the back of a car, driven to a Belarusian border town near Poland and released into no-man's land by the country's special services. She crossed into Poland and was taken to Warsaw by bus.