KANDAHAR, Afghanistan, July 18 (Xinhua) -- Casualties were feared after a car bombing and ensuing gun fire rocked outside provincial police headquarters in Kandahar city, capital of Afghanistan's southern Kandahar province, on Thursday, witnesses said.

"The blast struck the northern gate of the compound roughly at 4:35 p.m. local time. Following the explosion, militants tried to enter the facility," witness Mohammad Hashim told Xinhua.

Security forces have cordoned off the area. The blast caused panic among residents and the Crisis Response Unit (CRU) or special operation forces arrived at the site, the witness added.

Thick black smoke was seen rise above the site. No casualty reports were immediately available.

No group or individual has claimed reasonability for the attack so far.