Britons have been warned against making all but the most essential travel to Istanbul following Thursday's blasts.
Several British Consulate staff remain unaccounted for
The British Consulate and the HSBC bank headquarters in the city were hit in a series of explosions which killed at least 25 people and injured 400.
The British Consul-General Roger Short is among the dead.
UK Foreign Secretary Jack Straw is reported to be travelling to Turkey.
British Consulate chaplain Ian Sherwood confirmed Mr Short was one of the victims.
"I have been with the family of the Consul-General since it happened, and sadly the Consul-General is dead," he said, describing him as a "wonderful man".
Rev Sherwood said Mr Short had been entertaining the Archbishop of Canterbury only two days ago.
At least 14 people are reported to have been killed at the consulate.
Witnesses reported seeing a van driving straight at the consulate building before the explosion.
Shadow foreign minister Richard Spring, who visited Mr Short last month, said he was "devastated" by his death.
Britons were recommended not to travel to Istanbul unless on "essential business" but Foreign Office advice for the rest of Turkey has not changed.
The Foreign Office said there was "a significant threat from terrorism in Turkey".
In a statement to the foreign secretary the Queen said she was "deeply shocked" to hear of the attacks.
"Please pass my deepest sympathy to all caught up in these evil acts of terrorism", she said.
Home Secretary David Blunkett said 16 members of Scotland Yard's anti terrorist branch were flying to Instanbul on Thursday afternoon.
Foreign Office: 020 7008 0000
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They will be looking for forensic evidence which could lead them to the bombers, and assessing whether there are links with other attacks internationally, he said.
A spokesman for the Association of British Travel Agents said there were thought to be less than 100 UK tourists currently in Istanbul.
Millions of Britons visit Turkey every year but most tend to go to coastal resorts, such as Bodrum, many miles from Istanbul.
British Airways held an Istanbul-bound flight from Heathrow for 30 minutes while considering the situation on Thursday morning.
Flights will continue for the time being, but a BA spokeswoman told BBC News Online the airline would continually review its position.
The Foreign Office, in advice posted on its website on Thursday, said: "We advise against all but the most essential travel to Istanbul, until the situation becomes clearer.
It goes on to say: "We urge you to be vigilant in all parts of the country, and especially in the vicinity of potential terrorist targets."
British-based financial services company Aviva has closed one of its two Istanbul offices near to the HSBC building targeted in Thursday's attack.
Tony Blair has said the bombings in Istanbul reminded everybody of the "evil" terrorists posed to innocent people all over the world.
President Bush, in London on a state visit, also condemned the attacks.
Istanbul was hit by a number of explosions on Thursday morning, just days after 23 people died in two synagogue suicide bombings.
One blast wrecked part of the 15-storey headquarters of the London-based HSBC bank.
BBC correspondent Steve Bryant said the emergency services in Istanbul were struggling to get to grips with the aftermath of the explosions, which happened at 0910 and 0912 GMT.
He said eyewitness reports suggested a car, laden with explosives, rammed the main gate of the consulate and caused "devastation".
The British Ambassor to Turkey, Peter Westmacott, is travelling from Ankara to Istanbul.
HSBC said: "Two HSBC buildings have been struck by the bomb blasts across the city, including our head office in Levent.
"It is with deep regret that we have to confirm that there have been a number of fatalities. Our thoughts are with the bereaved, the injured and their families."
There was a series of explosions in the Turkish city
UK property firm Canary Wharf said it had boosted security around HSBC's London headquarters.
The British consulate in Istanbul was previously targeted in April when an explosive device was thrown at the building.
Also in April, three small devices exploded in the town of Izmir, one of which was near the British consulate.
No one was injured in either attack.
An information line for the Istanbul incident has been established on .