ANTWERP (AFP) - A Belgian court sentenced the leader of an Islamist group that sent extremist fighters to Syria to a 12-year jail term on Wednesday and imprisoned several other members in one of the largest cases of its kind in Europe.

Fouad Belkacem, 32, the chief of the Sharia4Belgium group, was convicted by a court in the northern port city of Antwerp of radicalising, recruiting and dispatching young men to fight holy war.

Forty-six members of the group originally faced charges of belonging to a terrorist organisation, but only eight were actually present during the five-month trial, with one deemed medically unfit to stand trial.

The rest were believed to be either still in Syria, or dead.

Muslim convert Jejoen Bontinck, 19 - whose father brought him home from Syria in a celebrated case and who later became a key prosecution witness - received a 40-month suspended sentence.

"Belkacem is responsible for the radicalisation of young men to prepare them for Salafist combat, which has at its core no place for democratic values," the judge said in his ruling. "Sharia4Belgium recruited these young men for armed combat and organised their departure for Syria."

The other members of the group were sentenced to between three and five years in prison, with some of the sentences being suspended. Security was tight at the court for the verdict, which came a month after two suspected militants were killed in Belgium during a huge anti-terror operation.

Belgium is the European country that has produced the most extremist fighters relative to its population size.

'SPIRITUAL LEADER'

Belkacem, a hardline ideologue known for his virulent street sermons and online videos, was the leading figure in persuading young Belgians to fight holy war in Syria. He had already been convicted in 2012 for incitement of hate against non-Muslims, and was portrayed by the others on trial as the spiritual leader of the group.

Sharia4Belgium rose to prominence in 2010 after a protest against a proposed ban on wearing the full-face Islamic burqa in public. It found fertile ground for recruitment in Antwerp,

Belgium's second biggest city, which has a large Muslim community, mainly from Turkey and Morocco, as well as one of Europe's biggest Jewish Orthodox communities.

Belgium remains on high alert following last month's terror major operation, which authorities said had smashed a cell aiming to kill police officers in public streets and at police stations.

Two suspected militants were shot dead in a raid in the eastern city of Verviers. An Algerian man extradited from Greece over his alleged involvement in the plot remains in detention but the suspected mastermind of the plot - Abdelhamid Abaaoud - remains at large. Sharia4Belgium has not been linked to the other cell.

Troops have been deployed outside major institutions in Belgium including government buildings, EU premises and diplomatic missions.

The raids happened days after the Paris terror attacks, in which homegrown militants attacked the offices of the Charlie Hebdo satirical magazine, shot a police officer and stormed a Jewish supermarket, killing 17 people.