A British national was among three people killed when a car bomb exploded near the main airport in Afghanistan's capital, the Foreign Office said.
The attack, which was claimed by the Taliban, also wounded 18 people.
Foreign Secretary Philip Hammond condemned the attack and said the British victim was a security contractor.
"This is the second attack in a matter of days for which the Taliban have claimed responsibility and I strongly condemn their cowardly actions," he said.
"These attacks must not stop the people of Afghanistan, with the support of the international community, working towards a more peaceful future."
The bombing appears to have targeted vehicles of the European Union police training mission EUPOL, which advises Afghan law enforcement authorities.
One of the mission's vehicles was hit by the blast, EUPOL spokeswoman Sari Haukka-Konu said.
She said all the EUPOL personnel "are in a safe place" with non-fatal injuries.
Two Afghan women, who were believed to be passers-by, were killed in the blast, said an Interior Ministry spokesman. Of the 18 wounded, eight were women and three were children.
The car bomb was detonated on a road a few hundred metres from the airport terminal early on Sunday morning.
Nearby homes and shops were damaged, and the road - choked with traffic throughout the day as vehicles pass through a slow-moving checkpoint into the airport - was strewn with the charred remains of a number of cars.
Rescuers carried wounded Afghan civilians from the scene, which was cordoned off by police.
A Taliban spokesman claimed responsibility for the attack in a statement emailed to media. The group, which has waged war in Afghanistan for more than a decade, launched an offensive in late April.
The insurgents also claimed responsibility for an attack on a Kabul guesthouse last week that left 14 people dead, including nine foreigners.
The Taliban has been seeking to gain new ground since the drawdown of foreign forces last year to a training force of about 12,500.
Originally posted at 13.11
