The helicopter was on a training flight in the port city of Gwadar, in Balochistan province, a navy spokesman said, a region where Islamabad has been battling a separatist insurgency for decades.

The Sea King aircraft crashed during takeoff at around 10:00 am local time (0500 GMT), after suffering an engine fire and losing its rear tail, according to a preliminary report shared with AFP by a military source.

The accident "possibly attributed to a technical malfunction" killed two officers and one enlisted man, the navy spokesman said.

Balochistan, Pakistan's largest province, is heavily militarised owing to huge Chinese investment schemes in the region which are regularly targeted by separatist militants.

Last September, six servicemen were killed in the province after their helicopter crashed in the small town of Khost.

A month earlier, six more servicemen including one of the army's top commanders were killed when their helicopter crashed during flood relief operations in Balochistan.