A clinic has been bombarded in the northern Afghan city of Kunduz, killing three Medecins Sans Frontieres (MSF) aid workers, with Nato investigating whether it was behind it, BBC News repotrs.

The medical charity says 30 people were also unaccounted for. There is no word on the nationalities of the victims.

A Nato statement said a U.S. air strike "may have resulted in collateral damage to a nearby medical facility".

The Taliban has clashed with government troops since its militants seized the northern city earlier this week.

Kunduz was the first major urban centre to fall to the Taliban in 14 years.

The medical clinic run by MSF was hit several times during "sustained bombing and was very badly damaged" at 02:10 local time (22:40 GMT) on Saturday, October 3 it said in a statement.

A statement from Nato said: "U.S. forces conducted an air strike in Kunduz city at 02:15 (local time)... against individuals threatening the force". But, it continues, the strike may have caused damage to a nearby medical facility.

Nato says it is investigating.