The 51-year-old was jailed for five-and-a-half years in 2016, and will serve the rest of his sentence under strict supervision orders having been released from Belmarsh top-security prison in southeast London.

He made no comment to reporters and photographers when leaving a probation hostel in the British capital.

Prisoners the UK are typically released early but with conditions attached to their activities outside custody.

Choudary is expected to return to his home in Ilford, east London, although he will not be able to use any internet-enabled devices without permission.

Other restrictions include bans on leaving Britain without permission and on attending certain mosques and he will only be allowed to meet with people approved by the police.

Choudary is the former head in Britain of Islam4UK or al-Muhajiroun, a now-banned group co-founded by Omar Bakri Muhammad that called for Islamic law in the UK.

For two decades, the former lawyer of Pakistani descent stayed on the right side of the law, becoming Britain's most prominent radical preacher.

- 'Pathetic groomer' -

Among those radicalised by Muhajiroun were the suicide bombers who killed 52 people on London's public transport system in July 2005, and the men who murdered soldier Lee Rigby in the capital in 2013, police say.

The court heard that Choudary had broadcast speeches recognising Abu Bakr al-Baghdadi as the leader of the Islamic State.

Choudary and his co-defendant Mohammed Rahman were arrested by officers from the Metropolitan Police's Counter Terrorism Command on September 25, 2014.

Former counter-terror police chief Mark Rowley insisted Friday that Choudary was not "some sort of evil genius".

"We have to be careful not to overstate his significance," he told BBC radio.

"At the end of the day, he is a pathetic groomer of others."

The father-of-five previously hit the headlines for organising a pro-Osama bin Laden event in London in 2011.

He also belonged to a group that burned poppies, the symbol of remembrance for deaths in war, during an Armistice Day protest in the British capital in 2010.

In a 2014 interview with AFP, Choudary called on Western journalists, civilians and troops in "Muslim countries" to "completely withdraw and allow us to implement the Sharia".

Former police terror chief Richard Walton called him a "hardened dangerous terrorist" who had had a "huge influence on Islamist extremism in this country".

Prisons Minister Rory Stewart has said he will be watched "very, very carefully" out of jail.