Afghan officials say a suicide bomb attack has killed at least three people and wounded 10 others in northern Afghanistan.

Officials say a suicide bomber blew himself up early Tuesday outside a building in the city of Kunduz.

Police say two other militants then stormed the building, resulting in a two-hour-long firefight with police. The fighting ended when the two militants inside the building detonated their explosives.

Three private Afghan security guards were killed in the attack.

Separately, Afghan officials said Monday a NATO airstrike killed four Afghan police officers and wounded two others in the country's east.

The governor of Nuristan province Jamaluddin Badar said coalition forces also detained 12 police officers after NATO aircraft bombed the police post in the Wama district.

Badar said the strike was based on wrong intelligence. He said the officers were wearing police uniforms and an Afghan flag was flying at the post when it was attacked.

NATO says it is “aware” of the statements by Afghan officials alleging friendly fire and is investigating the incident.