A UK court has sentenced British cleric Anjem Choudary to five-and-a-half years in prison for inviting support for the Islamic State of Iraq and Levant (ISIL) group.

Choudary, 49, was sentenced on Tuesday at London's Old Bailey court, following an earlier conviction of using online lectures and messages to encourage support for ISIL, also known as ISIS.

ISIL has been proscribed as a "terrorist group" in Britain since June 2014, making inviting support for the group a criminal offence punishable by up to 10 years in prison.

London-born Choudary ran into trouble in 2014 after his name appeared on an oath declaring the legitimacy of the "proclaimed Islamic Caliphate state".

Choudary said the oath had been made without his knowledge.

READ MORE: ISIL sympathisers say support is growing

Supporters of the preacher and his co-defendant Mohammed Mizanur Rahman - who received the same sentence - shouted "Allahu Akbar" (God is great) from the public gallery as the judge announced his decision.

The trial heard that the pair used speeches to urge support for ISIL after it declared a caliphate in the summer of 2014.

Judge Timothy Holroyde said Choudary was "calculating and dangerous" and had shown no remorse.

Dressed in a white robe, Choudary showed no emotion as the sentence was passed.

Choudary is the former head in Britain of Islam4UK or al-Muhajiroun, a now banned group

British police previously said that the group was suspected of being the driving force behind the 2005 London bombings, while Michael Adebolajo, one of the men who hacked to death British soldier Lee Rigby on a London street in 2013, had attended protests Choudary had organised.

The influence of the group, which was co-founded by Syrian-born cleric Omar Bakri Muhammad and called for Islamic law in Britain, is said to extend far beyond the UK.