A suicide bomber struck a foreign motorcade travelling through the Afghan capital Kabul on Tuesday. killing at least three NATO troops.
The huge blast, which the Taliban has claimed responsibility for, happened right next to the heavily fortified US embassy.
More than a dozen people were wounded.
Eyewitnesses described how the blast destroyed several cars.
Ahmad Ajman, who was in a nearby vehicle, said: “When I got out and started walking, the explosion happened. The same type of car that I was in was destroyed. The target was an American car. A lot people were killed and wounded and I saw them them being evacuated to hospital.”
The Taliban has stepped up attacks recently, exploiting the uncertainty over the results of the recent presidential election.
Analysts say this blast compounds fears that Afghan forces will struggle to maintain security after the withdrawal of NATO troops from the country at the end of the year.