We see their utter contempt for innocent life, says a defiant Bush

Tony Blair and George Bush condemned the attacks in Istanbul and warned the perpetrators that the bombings would make them even more determined to rid the world of terrorism.

Jack Straw, the Foreign Secretary, arrived last night in Istanbul, where he surveyed the scene of the blasts at the British consulate and the HSBC bank headquarters. A team of about 10 anti-terrorist police officers also travelled to the Turkish city to join the hunt for the bombers.

The bombings stunned Downing Street and the Foreign Office, and overshadowed a joint press conference by the Prime Minister and President. Mr Blair said: "When something like this happens today, our response is not to flinch or give way or concede one inch. We stand absolutely firm until this job is done - done in Iraq; done elsewhere in the world."

Asked if the atrocity was due to President Bush's state visit to Britain, Mr Blair replied: "What has caused the terrorist attack today in Turkey is not the President of the United States; is not the alliance between America and Britain. What is responsible for that terrorist attack is terrorism; are the terrorists."

Mr Blair said the right message to the terrorists was: "You are not going to defeat us because our will to defend what we believe is actually, in the end, stronger, better, more determined than your will to inflict damage on innocent people."

He added: "If they think that when they go and kill people by these terrorist attacks they are somehow going to weaken us or make us think let's shuffle to the back of the queue and hide away from this, they are wrong."

President Bush said: "The nature of the terrorists is evidenced once again - we see their utter contempt for innocent life. They hate freedom; they hate free nations."

He insisted the United States was making "good progress" against al-Qa'ida. "We are dismantling the operating management one person at a time," he said. "We are in an international manhunt."

Mr Blair's official spokesman said: "Today has been a grim day and a sad day."

The Queen sent a message saying she was "deeply shocked" at the attacks and expressed her sympathy to "all caught up in these evil acts of terrorism". Dr Rowan Williams, the Archbishop of Canterbury, who visited Istanbul and met Roger Short, the consul general, earlier this week, spoke of his "shock and grief".

Within hours of news of the blasts, the Foreign Office dispatched a rapid deployment team to Istanbul. Last night, they were liaising with consul staff, British nationals, Turkish government officials and journalists. Announcing the deployment of anti-terrorist police officers, Sir John Stevens, Metropolitan Police Commissioner, said the outrage bore "all the hallmarks of al-Qa'ida".

As Mr Straw's diary was cleared and his trip to Turkey rapidly organised, a government official admitted: "This is like a bad dream."

The blasts reinforced MI6 warnings to ministers, following last Saturday's attacks on synagogues in Istanbul, that Turkey was increasingly fertile territory for Islamic terrorism.

Earlier, in an emergency Commons statement, the Foreign Secretary denounced the "appalling acts of terrorism".

He told a sombre House: "Its too early to say who precisely was behind these explosions, but they have every hallmark of the cowardly and indiscriminate acts of terrorism of al-Qa'ida and its associates. These attacks are an affront to democracy and to the entire civilised world. They are an affront to people of every faith and religion in the world and we shall stand united with the international community in the fight against this appalling global terrorism. This threat will continue until it is defeated and, like Nazism, I am afraid there is only one thing we can do which is to work to defeat it."

Michael Ancram, the shadow Foreign Secretary, said: "Today has tragically shown, once again, that nowhere in the world is immune from the poison of international terrorism."