An Afghan police official says two gunmen dressed in police uniforms stormed into a police headquarters in northern Balkh province and opened fire, killing two officers.

Sher Jan Durani, a spokesman for the provincial police chief, said Sunday that the attackers were intercepted at the second security gate of the police headquarters in the provincial capital of Mazar-e-Sharif.

Durani said both attackers were killed by police. Nine other policemen were wounded during the gun battle.

No group claimed responsibility, but the Taliban have stepped up their attacks on Afghan security forces as foreign combat troops prepare to withdraw by the end of the year.

On Saturday, a suicide bomber in a police uniform attacked a police headquarters in the south, killing one officer.