A suicide bomber has killed at least 12 people in Maymana, the capital of Afghanistan's northern Faryab province.

"There are many dead and injured. The numbers I have for the time being are at least 12 killed, but this number is not definitive," Lt Col John Espen Lien told AP.

Most of the foreign forces in Faryab are Norwegians but Lien said no Norwegian soldiers in Nato's International Security Assistance Force (ISAF) were present when the bomb went off.

It is not clear whether the victims were civilians or military personnel.

Nato's Isaf force said that three service members had been killed in an explosion in northern Afghanistan but it was not clear whether the casualties were related to the Faryab blast.

More than 20 people were injured, some critically, in the explosion in Maynama.

Other reports suggested that most of the victims were including shopkeepers, women and children. The claims could not be verified.