Eight Afghan government soldiers have been killed in an attack in the south-eastern province of Khost.
The militiamen were working with US forces in the area
Military officials said the attack took place about 25 kilometres east of the town of Khost.
The BBC's Jannat Jalil says the soldiers died after the vehicle they were travelling in was blown up, apparently by a timed explosive device.
Local officials say two men have been arrested in connexion with the attack and handed over to US-led forces operating in the area.
The men were arrested after a car travelling on the same road was stopped.
The Afghans who died were members of a local militia who had been working with US forces in Khost.
A search is being conducted in a village near where the explosion happened.
There are frequent attacks on American military personnel in Khost and the Afghans who are working with them.
There have been a number of attacks on local forces in the past few months in the south-east which officials have blamed on former members of the Taleban regime.
This has led to fears that the Taleban may be trying to regroup or trying to destabilise the fragile process towards democracy.
Afghan officials say those carrying out the attacks are getting help from groups in Pakistan.
But Pakistan says it is doing all it can to seal the two countries' long, porous border.