A soldier from the US-led coalition troops was killed when attacked while on patrol in southern Afghanistan, a statement issued by the US military said on Thursday.

The statement, which was issued by the US military base at Bagram airfield, about 50 kilometres north of Kabul, did not disclose the nationality of the soldier, nor did it provide more details about the exact location of the incident.

Most of the soldiers serving under coalition banner are from the US.

Meanwhile, combined Afghan and international forces detained two militants and killed another during a raid in the south-eastern Paktika province on Wednesday, a separate US military statement said.

More than 3,500 people - mostly insurgents but including more than 180 international soldiers - have been killed in violence in Afghanistan so far this year, according to figures provided by Afghan and foreign military sources.