Six Afghan police and six militants were killed after Taliban attacked a police headquarters in Gardez city, capital of eastern province of Paktia on Sunday, the provincial police chief said.
The attack started after a terrorist rammed a truck bomb into front gate of Afghan National Police (ANP) 303 Spin Zar Police Zone at 6.15 a.m., Gen. Tooryalai Abadyani told reporters, Xinhua reported.
Five assailants armed with guns and suicide vests arrived by a vehicle and engaged with security forces shortly after the explosion, sparking heavy clashes lasting for hours, he added.
Over 20 civilians were wounded by shrapnel and flying glasses, he said, adding nine ANP officers were also wounded by the blast and gun firing.
The explosion also damaged nearby buildings of provincial police station and a police training centre as well as several houses.
Sunday's attack was the second terror incident in Gardez within weeks.
On May 20, two civilians, two police and five militants were killed after Taliban stormed a local bank in the city, 100 km south of Kabul.
Taliban militants claimed responsibility for the attack on Sunday.
Taliban-led insurgency has been on the rampage since late April when the Taliban launched their annual rebel offensive and intensified attacks across the country.