The prime minister has vowed to "defeat and destroy" the terrorists responsible for Thursday's attacks on the British consulate in Istanbul.

Blair's comments came ahead of reports that consul general Roger Short had been killed in the blast.

Addressing journalists the prime minister said the "fanatics of terror" had shown themselves to be "callous murderers" of innocent people.

"This is a time to show strength, determination and complete resolve," he said. "Once again we are reminded of the evil these terrorists pose to innocent people everywhere and our way of life.

"Once again we must affirm that in the face of this terrorism there must be no holding back, no compromise, no hesitation in confronting this menace, in attacking it wherever and whenever we can and in defeating it utterly."

At least 29 people were killed and 390 injured in the two attacks on British targets in Istanbul.

Sources on the ground say they expect the death toll to rise significantly throughout the course of the day.

The two explosions took place shortly after 9.00am.

According to the Associated Press news agency al Qaeda and Turkish Islamic militant group IBDA-C have claimed responsibility for the attacks.

Metropolitan Police chief Sir John Stevens described the blasts as "appalling" and announced that British anti-terror officers are being sent to the country.

The first attack took place outside the British consulate building - blowing out windows and destroying two outbuildings.

A second blast took place outside the HSBC bank in the city.

A spokesman for the bank said an unconfirmed number of its employees had been killed.

The terror attacks coincided with today's meeting between Blair and George W Bush.

The president said the attacks should stiffen the resolve to root out terrorists across the globe.

The prime minister went on to express his "deepest concerns and condolences" to those killed.

"Once again we are reminded of the evil that these terrorists pose to people everywhere," he said.

Blair said there could be "no hesitation" in confronting the menace of global terror networks.

In an emergency Commons statement Jack Straw told MPs that the Foreign Office was advising British nationals against non-essential travel to Istanbul.

Shadow foreign minister Richard Spring expressed his concern and sympathies to the victims of the outrage.

"Britain enjoys close and harmonious relations with Turkey we need to assist them with our expertise to deal with this new form of terrorism which is wholly alien to a secular society like Turkey," he said.

And he paid tribute to the work of the consul general.

"I was with him last month and saw at first hand his professionalism in doing an extremely important job in the key British Consulate in Istanbul. He showed me around the Consulate building which was being renovated," he said. "I am personally devastated by his death."

The Liberal Democrats' foreign affairs spokesman Menzies Campbell said Britain had to accept that it was now the target of terror groups.

"This is a shocking and tragic example of the willingness of terrorists to attack wherever and whenever they can to do the most damage," he said.

"It appears that British interests may have been specifically targeted. Those who represent the UK abroad are now clearly in the front line."

Some 23 people were killed in a recent bomb blast which ripped apart a synagogue in Istanbul. A group with links to al Qaeda took responsibility for that attack.