Passports are said to show Omar Khan Sharif (L) and Asif Mohammed Hanif
The British Government has vowed to assist Israel's investigation into a suicide bombing in Tel Aviv after Israeli authorities said two Britons were behind the attack.
Israeli officials say the suicide bomber, who killed himself and three other people in the explosion at a Tel Aviv cafe, and an accomplice who fled the scene were British citizens.
More than 50 people were injured in the bombing at a beachside bar called Mike's Place on Tuesday.
Israeli television showed passports alleged to belong to Asif Muhammad Hanif, whose family live in London, and Omar Khan Sharif, who is from Derby.
The Israeli prime minister's office claims Mr Hanif was the suicide bomber who died and Mr Sharif escaped the area after failing to detonate a second explosive device.
Foreign Office minister Mike O'Brien told the BBC the British Government would co-operate fully with the Israelis to establish who the bombers were.
"The Israelis are in consultation with us at the moment about getting some information and I understand the Home Office will do all it can to enable the Israelis to identify who these individuals were, if indeed they are British subjects.
"They certainly were carrying, it appears, British passports, therefore we need to help them get the one that's escaped and identify the other one," he said.
Prime Minister Tony Blair condemned the suicide bombing and his spokesman stressed that the overwhelming majority of British Muslims would deplore the incident.
A UK Foreign Office spokesman said it was in close contact with the Israeli Government and would give the Israelis any assistance requested.
The blast came just hours after new Palestinian Prime Minister Mahmoud Abbas won approval for his cabinet and vowed to crack down on militants.
Israel said the suicide attack represented a "complete failure" in security for the new administration.
Israeli ambassador to London Zvi Shtauber said there was no news on the whereabouts of Mr Sharif.
He told BBC Radio 4's Today programme: "We are doing an effort to find him, and we are very
appreciative of the British Government's readiness to fully cooperate with us on
that, and I am sure we will find him.
"According to the evidence that we have so far, it clearly suggests that they are British subjects.
"In my mind, no grievance, no claim, legitimate as it might be, and I am sure that the Palestinians have many justified claims, can justify this campaign of terror and atrocities directed only against civilians."
A fringe radical Muslim group in Britain, Al-Muhajiroun, defended the attack.
Let us be absolutely clear, the loss of innocent life is against the laws of humanity
Muslim Council of Britain
Its UK spokesman, Anjum Choudhury, could not confirm the men were from Britain but he said it would not surprise him as Muslims had an obligation to support Muslims in other countries in jihad or holy war.
But the Muslim Council of Britain, which says it represents more than 350 Islamic organisations and mosques in the UK, was swift to condemn Al-Muhajiroun.
Spokesman Iqbal Sacranie said Mr Choudhury's comments were inflammatory and would harm community relations in Britain.
Mr Sacranie added that it was "alarming" to think that young Britons could be involved "acts of such a ghastly nature".
"Let us be absolutely clear, the loss of innocent life is against the laws of humanity," he said.
And the BBC's community affairs correspondent Barnie Choudhury said Al-Muhajiroun had "minority support".
"Its view that the suicide bomb attack in Israel was justified will be condemned by the majority of Muslims in the UK," he said.
The BBC's James Reynolds in Jerusalem said the bombing followed a familiar pattern of attacks coinciding with apparent diplomatic advances towards peace.
The explosion did not delay the publication of a peace "roadmap" by international mediators.
Israeli and Palestinian leaders are now considering the peace plan.
Mahmoud Abbas was sworn in as prime minister just hours after the suicide attack.