Four Afghan police officers and six civilians were among the dead. Photo: BBC

Nato did not confirm the nationalities of the soldiers, but correspondents say US troops operate in the area.

Taliban insurgents said they carried out the attack, which also killed four Afghan police.

Witnesses said the attacker waited for troops to leave their vehicles before detonating the bomb.

At least six civilians were also killed and 60 people were wounded in the attack.

The bomber targeted a coalition convoy passing through a crowded part of Khost, reports the BBC's Quentin Sommerville in Kabul.

Spike in violence

He says American troops serve in the area - although an announcement on the nationality of the soldiers is still awaited.

Khost, like other parts of eastern Afghanistan, has seen a dramatic rise in violence.

In June, a suicide bomber killed 21 people including three US troops and a local interpreter in the city.

The attack drove a motorcycle laden with explosions to a joint Nato-Afghan military checkpoint set up in a crowded bazaar.

The Taliban-affiliated Haqqani network regularly mount large-scale attacks and suicide bombings in the area.

Over the weekend, a shooting at a checkpoint in eastern Afghanistan took the US military's death toll in the war past 2,000.

Three US soldiers and contractor were killed in the attack in Wardak province on Saturday, along with three Afghan soldiers.