The state-run Associated Press of Pakistan quoted a spokesman as saying "the crashed UAV (unmanned aerial vehicle) was on a routine training flight" when it went down. The plane is used for photography and surveillance, the report said.
China's official Xinhua news agency quoted local television channels as saying the crash resulted in a fire at the refinery. It quoted the navy spokesman as saying the drone crashed after a bird hit.
Geo News reported fire trucks and ambulances reached the site but quoted police as saying no one was injured on the ground. The extent of the fire was not known as the refinery area is in a no fly zone.
Xinhua said the Pakistani navy has increased monitoring after militants attacked the navy's main air station in the city in May, leaving 10 navy personnel dead.