FILE - This is a Friday, April 3, 2015 file photo of Anjem Choudary, a British Muslim social and political activist and spokesman for Islamist group, Islam4UK, speaks following prayers at the Central London Mosque in Regent's Park, London. Choudary nne of Britain's best-known radical preachers Tuesday Sept. 6, 2016 was sentenced to 5 ¬? years in prison for encouraging support for the Islamic State group. The 49-year-old Choudary has been one of the best-known faces of radical Islam in Britain for years. Ôªø (AP Photo/Tim Ireland, File)

LONDON - One of Britain's best-known radical Islamic preachers was sentenced Tuesday to 5 1/2 years in prison for encouraging support for the Islamic State group.

Anjem Choudary has been one of the best-known faces of radical Islam in Britain for years, leading groups under names including al-Muhajiroun, Islam4UK and Muslims Against Crusades.

Several people who attended Choudary's rallies and events have been convicted of violent attacks, including the pair of al-Qaida-inspired killers who ran over British soldier Lee Rigby and stabbed him to death in 2013.

His supporters shouted "Allahu akbar," the Arabic phrase for "God is great," as Choudary was sentenced at Central Criminal Court in London.

Until he was charged under the Terrorism Act last year, the 49-year-old firebrand preacher gained attention for headline-grabbing activities that provoked outrage but stayed within the bounds of the law. They included protesting outside the U.S. Embassy on the anniversary of the Sept. 11 attacks and burning memorial poppies on the annual Remembrance Day honouring slain service members.

But the London-born preacher ran into trouble in 2014 after his name appeared on an oath circulating online that declared the legitimacy of the "proclaimed Islamic Caliphate State." Choudary denied encouraging his followers to support the Islamic State group and said the oath was made without his knowledge.

Police said Tuesday that evidence from authorities in Indonesia established that Choudary and co-defendant Mohammed Mizanur Rahman "were key in the publication of their oath of allegiance."

"We have watched Choudary developing a media career as spokesman for the extremists, saying the most distasteful of comments, but without crossing the criminal threshold," Dean Haydon, head of the Metropolitan Police's Counter Terrorism Command, said. "At last we had the evidence that they had stepped over the line and we could prove they were actively encouraging support of (Islamic State.)"

Evidence presented during the trial showed that Choudary broadcast speeches online explaining his rationale for recognizing Abu Bakr al-Baghdadi as the leader of Islamic State or Daesh.

"Both men were fully aware that Daesh is a proscribed terrorist group responsible for brutal activities and that what they themselves were doing was illegal," Sue Hemming, the Crown Prosecution Service's head of counter terrorism, said.

Both Choudary and Rahman, 33, were found guilty of inviting support for IS between June 29, 2014 and March 6, 2015. Rahman also was sentenced to 5 1/2 years.

News from © The Associated Press, 2016