British police yesterday arrested nine men under anti-terrorism laws and warned that bombers who tried to detonate explosives on London's transport system last week could strike again.
Sir Ian Blair, the Commissioner of London's Metropolitan Police, said that, with three of last week's four would-be bombers still at large, "it does remain possible that [ they] will strike again". He added: "It does also remain possible that there are other cells that are capable and intent on striking again."
His warning came as police officers mounted their biggest ever deployment on London's rail network in a highly-visible show of strength aimed at reassuring commuters unnerved by two waves of bombs attacks in three weeks.
But the deployment did not mean an end to disruption for Londoners. An underground station was evacuated and part of a main east-west line closed in a security alert last night.
A British Transport Police spokeswoman said that Southwark station had been closed and Jubilee Line services suspended between Waterloo in central London and Canary Wharf.
Police have dealt with dozens of security alerts across London since the July 7th bombings and an attempt to bomb three trains and a bus on July 21st.
Police yesterday continued to question Yasin Hassan Omar, a 24-year-old Somali national who was arrested on Wednesday night and is suspected of trying to detonate a bomb at Warren Street underground station.
The nine men were arrested in raids on two addresses in Tooting, south London, but police indicated that none of the three prime suspects in the July 21st attacks was among them.
On Wednesday evening three women were arrested at a flat in a block near Stockwell underground station - where three of the suspected bombers boarded trains - on suspicion of harbouring offenders.
Some neighbours in the block of flats said that they recognised CCTV images issued by the police of the man they believe tried to detonate a bomb on an underground train near Shepherd's Bush station.
Police sources said they could not rule out the possibility that one or more of the men had already fled abroad. But one source said: "Our feeling is still that they are more likely to be in the UK."
Investigators also confirmed that they were still removing material for forensic examination from the flat in New Southgate, north London, used by Mr Omar, following reports that a large stash of chemicals which could have been used for making bombs had been stored there.
"We are taking away quite a lot of material from there. It looks like it's a significant address for us," an officer said.
Commissioner Blair warned: "This is not the B team. These weren't the amateurs. They made a mistake, they made one mistake. We are very, very lucky."
He said that his detectives were in a race against time to find the July 21st bombers: "Either we find them, or they are capable of carrying out more atrocities. That's why we are pursuing them with such urgency."
He told reporters that there had been 5,000 calls to the anti-terrorist hotline, police had viewed 15,000 CCTV tapes and 1,800 witness statements had been taken.
Muslim groups said yesterday that attacks on Asians and religious minorities in London have risen by more than 500 per cent since the suicide attacks on the capital three weeks ago.
Across Britain, one man has been murdered, one mosque firebombed, a Sikh temple attacked and other buildings and individuals targeted, according to the Muslim Safety Forum (MSF), an umbrella group of Muslim organisations which advises the police.
Commissioner Blair said that the police were determined to tackle racially and religiously motivated crimes, but he insisted that such offences remained at a very low level for such a large city.