Fouad Belkacem Sharia4Belgium
Fouad Belkacem, the leader of radical Islamist group Sharia4Belgium has been sentenced to 12 years in jail.NICOLAS MAETERLINCK/AFP/GettyImages

An Antwerp court sentenced to 12 years in jail the leader of a radical Islamic organisation that worked as a recruiting centre for jihadist groups fighting in Syria in one of the biggest terror trial in Belgium's history.

Fouad Belkacem and another 44 Islamist militants were found guilty of terror-related offences over their connection to Sharia4Belgium, a dissolved group deemed by the court as a terrorist organisation that worked to violently replace democracy with a strict interpretation of sharia law.

The group allegedly brainwashed numerous young Muslims, recruiting them to join the Islamic State (Isis) or the al-Qaeda affiliate Nusra Front.

A total of 46 people were originally indicted, but only a handful, including Belkacem, appeared in court, as most are believed to be fighting or having died in Syria.

Forty-five were given sentences, some suspended, ranging from three to 15 years behind bars.

Belkacem, who was led into court in handcuffs by police in body armour, smiled when the judgment was read out.

Sharia4Belgium was formed under the guidance of British hate preacher Anjem Choudary, as he was running his Islam4UK group. In November, Choudary described Belkacem to The Times as a "dear friend of mine", expressing the desire of see him out of jail.

The sentencing came amid soaring terror fears in the country.

Belgium's terror threat was raised to its second-highest level in the wake of the January attacks that left 20 people, including three gunmen, dead in neighbouring France.

Last month, more than 10 people were arrested and two killed in an anti-terror raid against a jihadi cell allegedly planning to kill policemen in the street and at police stations in the eastern Belgian city of Verviers.

Last week, a local newspaper received a threatening letter signed by Isis vowing to carry out bomb attacks retaliation for the Sharia4Belgium trial.

Belgium has been the scene of Islamist attacks in the past and is said to be the European country with the highest pro-capita rate of extremists fighting in Syria and Iraq.

Mehdi Nemmouche, a French jihadist who fought in Syria, shot dead four people at the Brussels Jewish Museum in 2014.