BRITISH CITIZEN KILLED

A witness saw at least one survivor being led away from the charred shell of the British embassy vehicle by a member of the British security force.

"I am deeply saddened to confirm that a British national civilian security team member and an Afghan national working for the embassy were killed in the incident," Foreign Secretary Philip Hammond said in a statement, adding that another Briton had been injured.

G4S, the world's biggest security firm, later confirmed one of its staff had been killed in the blast and another injured.

"Next of kin have been informed and we will continue to provide them with support," a company spokesperson said.

The Afghan interior ministry initially reported that the blast was caused by a suicide bomber on a motorcycle, but later said the attacker had been in a car.

Since Monday, when two American soldiers were killed in a powerful blast close to the airport, there have been at least five high-profile attacks in Kabul.

Last year a 25-year-old American diplomat was killed in an attack on a convoy in the east of the country, and the US consulate in western Herat province was attacked with a truck bomb. In May, the Indian consulate in the same province was targeted by insurgents with rocket-propelled grenades and suicide vests.