Germans 'killed in Afghan blast'

The source of the explosion was believed to be an improvised explosive device often used by insurgents.

The Taleban said recently they were targeting Kabul and the city has seen many lethal bombings in recent months.

Police bus

The convoy was reportedly 10km (six miles) south-east of Kabul on the Jalalabad road and travelling to a shooting range when it was hit.

One of the vehicles was blown onto its side.

Helicopters arrived at the scene and took the bodies away, witnesses said.

The head of Kabul police's criminal investigation department, Alishah Paktiawal told the AFP news agency: "There was an explosion. Three people have died and one has been injured."

The German embassy said it could not yet comment.

Nato's International Security Assistance Force (Isaf) said it was aware of a bomb attack but could not comment on casualties.