An Afghan police commander has killed three US soldiers in the southern province of Helmand.

Officials claim the men, who were all American special forces members, were shot on Thursday night after guns were turned on them during a dinner to discuss security.

A senior Afghan official said: "During dinner, the police commander and his colleagues shot them and then fled. The commander was Afghan National Police in charge of local police in Sangin."

A spokeswoman for Nato-led forces in the country confirmed the incident but said it was too early to say whether it was a rogue shooting or due to insurgent infiltration.

So-called green on blue shootings, in which Afghan police or soldiers turn their guns on their Western colleagues, are a major problem as combat soldiers prepart to hand over to Afghan forces in 2014.