"The plane has been totally gutted and there are no survivors," lieutenant Colonel Noor Alam who supervised rescue operation told reporters.
The plane was believed to be carrying about 20 people, mostly Pakistanis, he said, adding that bodies have not yet been identified.
It was not immediately clear if there were any foreigners on board, he said.
So far, 12 bodies, gutted completely and unable to be identified, have been recovered and efforts to recover the remaining are underway, Noor Alam said.
Reports from CAA authorities confirmed that at least 20 people were on board who have been feared dead as the wreckage caught fire after crash. Accident took place at 7:15am.
Rescue teams, police, airport security force, ambulances arrived on the accident site and kicked off rescue and relief operations. Plane crashes away from residential area.
Thick smoke was seen emitting from plane while firefighters tried hard to bring fast raging flames under control.
The airplane was of a private company and had been chartered by a US company working on an oil field in Karachi. Two crewmembers and a technician were also on plane.
The crash took place due to engine failure as the pilot tried to contact control tower complaining there was flaw in one engine of plane, reports said.
CAA official Pervez George said the aircraft was carrying company employees to an oil field at Bhit Shah in the southern province of Sindh, of which Karachi is the capital.
"It was a small plane and there were about 20 people on board. It was a privately-owned aircraft belonging to an oil company," George told .
"Soon after they left, they contacted the airport control tower and said there was a problem in one of the engines. The plane was directed to return and soon after it crashed," he said.
