BRUSSELS — Belgian police raided 48 homes across the country on Tuesday and detained six men after a year-long investigation into an Islamist group suspected of recruiting fighters for Syria's civil war.

Prosecutors said Fouad Belkacem, the leader of Sharia4Belgium, was one of the six, but declined to give details on the others, beyond saying one had returned wounded from Syria.

Prosecutor Eric Van der Sypt told a news conference that he and his colleagues were investigating whether Sharia4Belgium constituted a terrorist organization, membership of which could lead to a jail term of up to 10 years.

"The investigation shows that Sharia4Belgium is part of a broad international jihadist movement," Van der Sypt said.

Foreign Islamist insurgents are increasingly playing a role in Syria's civil war, which started in March 2011 with street protests against the four-decade rule of the family of President Bashar al-Assad.

Sharia4Belgium is accused of giving ideological and combat training, organizing violent activities in Belgium and recruiting Islamist fighters for conflicts abroad. Van der Sypt said prosecutors were aware of 33 people with links to the group who were either in or on their way to Syria.

"The recruitment occurred, for example, by youths being spoken to on the street and then invited to private meeting places in Antwerp," he said.

Police seized computers, mobile telephones and money in the house searches, mostly in the northern province of Antwerp.

The Syrian conflict pits the Sunni Muslim majority against Assad's supporters among his Alawite sect, an offshoot of Shiite Islam, and has prompted both Sunni and Shi'ite militants from elsewhere to fight in Syria.

Sharia4Belgium is a Salafist group opposed to Assad. Belkacem, who described himself as the spokesman for Sharia4Belgium, was convicted last year of inciting hatred and violence against non-Muslims and ordered to wear an electronic monitoring ankle band.