Madrid (CNN) -- Swooping in at 4 o'clock in the morning, Spanish police arrested six Spanish men on suspicion of recruiting and sending 26 radical Islamic fighters for terrorist groups in Syria, Mali and Libya, the Interior Ministry said Friday.
The arrests came in the Spanish enclave of Melilla, on Morocco's north coast, where a Spaniard and two Frenchmen were arrested just last March on similar charges.
The suspected leader in the cell disrupted on Friday had returned to Spain after fighting in Syria and training in a terrorist camp in northern Mali, the Interior Ministry said.
The movement of Islamic militants from Europe and North Africa to conflict zones such as Syria, Mali or Libya -- and their eventual return to Spain to potentially carry out terrorist attacks -- has been a prime concern for authorities battling terrorism.
The cell disrupted on Friday had recruited and sent at least 24 Moroccans and two Spaniards to conflict zones, according to authorities. But it was planning to expand its activities, to acquire weapons and manuals for preparing explosives, the Interior Ministry said, "which would have increased their level of danger, turning them into a serious threat to national security."
The latest arrests coincide with the final day of an Interpol conference, held in Granada, Spain, this week, on the problem of terrorist fighters who cross international borders. More than 130 security experts from 33 nations are attending, a separate Interior Ministry statement said.
The suspected leader of the cell disrupted on Friday is Benaissa Laghmouchi Baghdadi, 42, who spent about eight months in Syria and recently returned to Spain, via Mali, said an Interior Ministry spokesman, who by custom is not identified. He was among the first Spaniards to be detected as working with terrorist groups in the broad Sahel region in northern Africa.
The other five suspects arrested were identified as Mustafa Al Lal Mohamed, 42; Kamal Mohamed Dris, 32; Rachid Abdel Nahet Hamed, 37; Mohamed Mohamed Benali, 26; and Mustafa Zizaoui Mohand, 26. All of the suspects were being flown to Madrid, to be taken to National Police headquarters. Arraignments are expected on Monday.
Last January, a suspected Islamist militant returning to Europe from the war in Syria was arrested at the Malaga airport in southern Spain as a potential "threat to national security," the Interior Ministry said in a statement at the time.
March 11 marked the 10th anniversary of the Madrid train bombings that killed 191 people and wounded more than 1,800.
The Spanish courts convicted 14 Islamic militants for their roles in the bombings on morning commuter trains, along with four Spaniards who trafficked in explosives used in the attacks. A further seven key Islamist suspects blew themselves up three weeks after the train attacks as police closed in on their hideout in a Madrid suburb.
Spain has arrested more than 472 suspected Islamic militants since the train bombings. There are now more than 1,800 police and security officials dedicated to fighting terrorism, far more than at the time of the attacks, Interior Minister Jorge Fernandez Diaz said last March.
On Thursday, Spain's National Court sentenced Mudhar Hussein Almalki, 53, a Saudi national, to eight years in prison for of membership in a terrorist organization, according to a copy of the sentence viewed by CNN.
He was convicted of using the Internet, from his home in Valencia, Spain, to spread terrorist ideology with the aim of training militants, for at least six years until his arrest in 2012, the sentence said.
He was legally residing in Spain at the time and had no prior criminal record, the sentence said.
Spain is on a Level 2 anti-terrorist alert, unchanged since 2009, on a scale of four terrorist prevention levels. Level 2 signifies a "probable risk" of another attack, the Interior Ministry said.
Melilla is a Spanish city with about 85,000 residents. It was in the news earlier this week when about 1,000 sub-Saharan migrants rushed the fence from the Moroccan side, and some 500 made it over and into Spain, with the aim of finding work in Spain or in the European Union, authorities said.
As police escorted the suspects from the homes where they were detained, crowds formed and some people heckled the police for making the arrests, an Interior Ministry spokesman said.