Police have arrested a ninth man as part of their counter-terrorist operation in south-east England.
Police continue to search a house in Crawley
Detectives said the 27-year-old Briton was arrested in Crawley, West Sussex - the fourth man arrested in the town.
He was held on Thursday evening on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism.
The other eight were arrested in the South East on Tuesday and officers have three more days to interview them.
Detectives in west London also seized half a ton of fertiliser often used as an explosive.
The latest suspect has been taken to a central London police station where he will be interviewed by officers from the Metropolitan Police Service Anti-Terrorist Branch.
Meanwhile, a man has also been detained by police in Canada in connection with alleged terrorist offences in London.
Mohammed Momin Khawaja was arrested at work in Ottawa on Monday when police also searched his house and briefly detained two of his relatives.
The 24-year-old software developer has been charged with aiding a terrorist group and facilitating terrorist activity in the Canadian capital and at or near the City of London, since last November.
He is due to appear via video link before a court in Ottawa on Friday.
Scotland Yard will not say whether the arrest is linked to the operations in England.
In a further development Mr Khawaja's 62-year-old father has been detained in Saudi Arabia, where he was working at a technical college.
Safeguarding the UK
Meanwhile, the Muslim Council of Britain has said it has had an "overwhelmingly positive" reaction to its calls for mosques to help in the fight against terror.
Scotland Yard echoed the plea, and said Islamophobia would not be tolerated.
Prime Minister Tony Blair welcomed the move, saying it made clear terrorism "has nothing to do with the true message of Islam".
Sermons will be delivered on Friday saying terrorism has no place in Islam, while booklets being printed will remind Muslims of their obligation to help safeguard Britain's security.
However, Sheikh Omar Bakri Muhammad, who leads the London-based group Al-Muhajiroun, told BBC Radio 4's Today programme that helping the police would mean renouncing Islam.
Forensic teams were called
He said: "Muslims have a unique way of life. Co-operating with the authorities against any other Muslims, that is an act of apostasy in Islam. Muslims in Britain have the right to defend themselves, but without the use of violence."
But Shahid Malik, a member of the Labour Party's national executive committee, told the same programme Sheikh Omar only represented 200 people.
"Those involved in terrorism are not following the Muslim and Islamic way. Anybody involved in crime, it is the duty of all citizens to help the police and report them," he said.
The eight arrested in the Tuesday's raids were aged between 17 and 32 and are thought to be UK citizens of Pakistani descent.
Under the Terrorism Act 2000 they can be held for up to two weeks, but must then be charged or released.
Ansar Khan from Crawley, father and uncle of two men who were arrested, said there was "absolutely no truth" in the allegations against them.