They said ambulance workers removed five charred bodies from the wreckage and four more were believed trapped inside two Hercules C-130 transport aircraft which caught fire at the Chaklala base, about 15 km from the capital.

There was no official comment on the cause of the accident at the airstrip, which is next to Islamabad's international airport.

Airport sources said the accident occurred when one of the aircraft, which was trying to land, collided with the other, which was taking off.

A police spokesman said the blaze, which was brought under control, would not affect operations at the civilian airport, a terminus for international and domestic flights.