The soldiers identified the firing point and they returned fire

Isaf spokesman Graham Dunlop

But six British soldiers reported that they had returned fire after having been shot at as they manned an observation tower.

The British-led peacekeepers have so far been warmly welcomed in the Afghan capital, but BBC correspondent Michael Voss says this incident risks souring that positive relationship.

Curfew

The family said they had defied a strict night time curfew (from 2130 local time) to take 21-year-old Faria Ishaq to hospital to give birth when they came under fire at about 0120 local time.

Faria Ishaq was being taken to hospital

They say her brother in-law Amaun, 20, was killed outright. Her husband, Mohammed Ishaq, 25, her mother-in-law and a neighbour, who was driving, were all injured.

Mr Ishaq said the family fled home where his wife gave birth before a joint patrol of peacekeepers and Afghan police arrived at first light. The baby boy appeared to be healthy, he said.

"We did not have any weapons of any kind," he said, adding: "We did not hear any gunfire until we ourselves were shot."

The patrol found a car riddled with gunshots near the family's house.

Captain Graham Dunlop, a spokesman for International Security Assistance Force (Isaf) in Kabul, said: "The soldiers identified the firing point and they returned fire."

Captain Dunlop said the patrol had also found the dead man, a woman and baby and two other people in the house.

They were all taken to hospital for treatment for injuries and no weapons were found at the house, he said.

Removed from post

The paratroopers, from the 2nd Battalion, have since been removed from the Kabul observation post and a full investigation is under way, a Ministry of Defence spokesman said.

British soldiers have been in Afghanistan since December, leading the 4,000-strong Isaf force.

Lieutenant Colonel Neal Peckham said it was the first incidence of Isaf troops coming under fire.

The incident comes at a time when Afghanistan's interim leader, Hamid Karzai, is pressing for an increase of the number of peacekeeping troops and to expand their presence throughout the country.