Radical preacher Abu Qatada has been arrested for allegedly breaching his bail conditions, days ahead of the Government's latest deportation bid in court.
UK Border Agency officials arrested Qatada yesterday, following raids by the Metropolitan Police Service Counter Terrorism unit.
Searches at two residential homes and a business began on Thursday, while a search on a third property is ongoing, Scotland Yard said.
However no arrests have been made in connection with the police investigation.
A Home Office spokesperson said: "The UK Border Agency arrested a 52-year-old man from north London for alleged breaches of his bail conditions imposed by the Special Immigration Appeals Commission (SIAC)."
He added that the breach will be considered by SIAC at the earliest opportunity.
A spokesman for Scotland Yard said: "Searches at a residential addresses in north west London, a residential address in west London and a business address are in north west London have been completed.
"A search at a residential address in north-west London is ongoing."
The searches were carried out in connection with ongoing inquiries by the Counter Terrorism Command, he added.
Qatada, who has been convicted of terror charges in Jordon, is due to appear at the Court of Appeal on Monday for Home Secretary Theresa May's bid to overturn a judge's decision to allow him to stay in the UK.
Qatada was arrested outside his home by the UKBA, The Sun has reported.
Pictures show him being escorted out of his house by officials with his hands hidden under a jacket.
Raids on his home by terror police began at 6.30am on Thursday, Scotland Yard said, and were followed by his arrest by the UKBA yesterday.
Once described by a Spanish judge as "Osama bin Laden's right-hand man in Europe", Qatada has used human rights laws to fight deportation for more than a decade.
SIAC decided last November that Qatada could not lawfully be deported to Jordan, where he was convicted of terror charges in his absence in 1999.
SIAC judges ruled there was a danger that evidence from Qatada's former co-defendants Abu Hawsher and Al-Hamasher, said to have been obtained by torture, could be used against him in a retrial in Jordan.
He was granted bail following the ruling by three SIAC judges and released from HMP Long Lartin, returning to his family home in London.
However, on Monday the Government will challenge the decision in front of three Court of Appeal judges led by Lord Dyson, the Master of the Rolls.