AirAsia said 31-year-old passenger Liew Siaw Hsia went into labour on Wednesday's flight from the northern island of Penang to Kuching on Borneo island.

The aircraft made an emergency diversion to the Malaysian capital but the baby arrived just before landing, delivered by a doctor who was on board and who was assisted by the airline's flight attendants.

"The baby was safely delivered when flight AK 6506 was approaching Kuala Lumpur for landing at 2,000 feet," the airline said in a statement, adding that mother and baby were taken to a nearby hospital following touchdown.

"To celebrate this momentous occasion, we decided to present both mother and child with free flights for life," said AirAsia's director of operations Moses Devanayagam after visiting them in hospital.