Anjem Choudary, Britain's most high-profile hate preacher whose followers have been linked to numerous militant plots across the world while he has escaped justice, is facing jail after being found guilty of supporting Islamic State.

Choudary, 49, and his close associate Mizanur Rahman, 33, were convicted at London's Old Bailey of using online lectures and messages to encourage backing for the group which controls large parts of Syria and Iraq.

Prosecutors said that in postings on social media, Choudary and Rahman had sought to validate the self-proclaimed "caliphate" declared by ISIS leader Abu Bakr al-Baghdadi and that Muslims had an obligation to obey or provide support to him.

Both men were found guilty last month, but their convictions could not be reported until today for legal reasons. The men, who denied the charges, are due to be sentenced in September.

Following years in which he avoided arrest despite his apparent sympathy for extremism and links to some of Britain's most notorious terrorists, Choudary was convicted after jurors heard he had sworn an oath of allegiance to ISIS.

Choudry reportedly has links to one of the men who killed Lee Rigby in 2013, Michael Adebolajo, and the Islamist militant Omar Bakri Muhammad.

Choudary and Rahman face up to 10 years in jail for inviting support for a proscribed organisation.

Prosecutor Richard Whittam QC said: "The prosecution case is that whichever name is used, the evidence is quite clear: when these defendants were inviting support for an Islamic state or caliphate they were referring to the one declared in Syria and its environs by Ibrahim [Abu Bakr] al-Baghdadi at the end of June 2014. Terrorist organisations thrive and grow because people support them and that is what this case is about. Do not confuse that with the right of people to follow the religion of their choice or to proclaim support for a caliphate."

In one audio clip lasting over an hour, uploaded to Choudary's YouTube channel on 9 September 2014 and titled How Muslims Assess the Legitimacy of the Caliphate, Choudary begins by explaining why he sees Islamic State as meeting the criteria for a legitimate Islamic caliphate. "The lesson from this narration is that obedience to the caliph is an obligation, if they rule by the sharia. And to obey them obviously means they must be established," Choudary said.

"I would just say...you know, for people who want to live under sharia law, obviously this is a great thing, and for those people who say we are promoting Isis, they are not even called Isis any more. Rather, you have an Islamic state where you have millions of people who are governed by the sharia law and I don't think it is against the law to go and live there and want to abide by sharia law."

Additional reporting by Reuters.