Aspokesman for the city's health department said Aynur Erkoca had suffered severe head injuries in the blast on Thursday at the headquarters of the British-based banking giant HSBC, which occurred minutes before a similar attack at the British consulate.
Among those killed in the bombings, which came just five days after a twin bomb attack on two synagogues, was the British consul general Roger Short, while some 450 were injured.
The Istanbul attacks came as US president George Bush was on a four-day state visit to the United Kingdom. At a joint news conference with British prime minister Tony Blair, Bush used news of the Turkish bombings to justify the US-led "War on Terror".
He claimed that US forces were succeeding in hunting down members of the al-Qaida network and their associates around the world.
In Istanbul, Turkish Foreign Minister Abdullah Gul, said his country's security forces had arrested several people in connection with the attacks, but he did not disclose further details.