British home secretary Charles Clarke has called European interior ministers to a special terror summit in Brussels next Wednesday.
He acted yesterday on the suggestion of the Spanish government as members of Europol, the European police intelligence exchange agency, joined British investigators in London last night to help collate information which might enable police to identify those responsible for Thursday's four bomb attacks in which more than 50 people died.
Police revised the death toll upward yesterday, while confirming that a total of 13 people died in the explosion on a double-decker bus at Tavistock Square alone and as the search for more bodies continued.
While the painstaking finger search for forensic evidence continued at the scenes of the explosions, police said the first indications were that each of the four devices contained less than 10lbs of explosive, capable of being carried in a rucksack - the modus operandi employed by the Madrid terrorists.
Metropolitan Police commissioner Sir Ian Blair said that while there was nothing to rule out the possibility, there was so far "absolutely nothing" to suggest the bus blast had been the work of a suicide bomber.
Anti-terrorist police will therefore be working on the assumption that those responsible for the outrage may still be in or around London.
Last night, security was high at British ports and airports as Sir Ian conceded that while it was "blindingly obvious" a terror cell had been at work in Britain, he did not know if they were still in the country, abroad or dead.
Taoiseach Bertie Ahern acknowledged yesterday that some al-Qaeda sympathisers were living in Ireland. They were watched by the gardaí, said Mr Ahern and there was no evidence to link them to the London bombings.
Mr Clarke's decision to invite his counterparts to review progress on EU-wide counter-terrorism measures followed his earlier refusal to rule out an al-Qaeda link to Thursday's attack.
It also coincided with a warning from London lord mayor Ken Livingstone that other world capitals could be targets regardless of their position on the Iraq war and that Londoners would probably have to remain vigilant "for the rest of our lives".
At a joint press conference with Sir Ian, Mr Livingstone dismissed suggestions that British foreign policy could have been the motive for the attacks saying: "I think any great world city will be a target for terror because they want the oxygen of publicity."
Sir Ian also stressed that the attacks which left more than 700 injured were on citizens of all nations, including people from Australia, China, Poland, Portugal, Sierra Leone and, it was later confirmed, Ireland.
Mr Livingstone announced that a book of condolences would be opened at City Hall on Monday and that a London bombing relief fund would be made available for the families of the victims and the injured. A book has also been opened at the British embassy on Merrion Road, Ballsbridge, Dublin.
Mr Livingstone echoed Queen Elizabeth's praise for the stoicism of Londoners, as he and the commissioner promised a full return to "business as usual" in the capital on Monday. The queen visited the wounded and said the bombers would not change the British way of life.
Central London was quiet and subdued, with some schools remaining closed and many people electing to work at home or take the day off, while some people travelling by tube admitted to some fear and apprehension.
Promising the "implacable resolve" of the police to "bend every sinew" to find those responsible, Sir Ian said he was proceeding on the basis that the attacks were the work of a terrorist cell rather than one individual.