An Afghan policeman shot dead two US-led soldiers today outside a US military base in Khogyani district, Nangarhar.
The incident occurred as Nato and Afghan soldiers fired at hundreds of people rallying in front of the base, killing two protesters.
An Afghan security official who spoke on condition of anonymity said: "There was a protest in front of a military base. An Afghan policeman fired at the foreign troops and killed two of them."
He added that he did not know what happened to the alleged gunman after the shooting.
Protests erupted across Afghanistan on Tuesday, a day after US troops incinerated copies of the Koran at the US military base outside Bagram.
As Aslef's annual assembly of delegates begins in Edinburgh tomorrow the general secretary explains the challenges his members - and workers across the country - face