Six soldiers serving with the Nato-led force in south Afghanistan have been killed, the alliance has announced.

They died when the vehicle they were traveling in hit an explosive device, a statement from Nato's International Security Assistance Force (Isaf) said.

One other soldier was injured. The nationalities of the dead and injured have not yet been released.

This is the worst single incident for the Nato force in Afghanistan for several months.

Worst year

An Isaf spokeswoman told the BBC there had been no civilian casualties and that all signs pointed to the Taleban.

"Certainly it lends itself to the type of tactic that Taleban extremists use," Lt Col Angela Billings said.

"Because they cannot beat us conventionally or tactically, they resort to this type of tactic in order to hide in the shadows."

British and Canadian troops make up most of the Isaf forces in the south.

"The Ministry of Defense is not aware of any UK involvement," said a British government spokeswoman referring to the latest incident.

The Taleban are maintaining strong opposition to Nato, particularly in the south and east.

Last year saw the worst fighting in Afghanistan since coalition troops ousted the Taleban in 2001 with some 4,000 people believed to have been killed - about a quarter of them civilians.

Helmand has been the focus of a recent operation by Isaf troops against militants.

About 100 fighters have been killed in it so far, officials say.

Photo caption

UK troops in Helmand