The pilots of a hijacked Malaysian airliner were both shot dead just before it plunged into a mangrove swamp last December killing everyone on board, an official report said yesterday.

The investigation shed no light on who seized the plane, or the motive. The Boeing 737 of the Malaysian Airline System was carrying 93 passengers and seven crew members when it crashed Dec. 4 in Malaysia's Johore state, just north of Singapore, during a flight from the resort island of Penang to Kuala Lumpur.

The dead included Malaysian Agriculture Minister Datuk Haji Ali Ahmad, the Cuban ambassador and a number of Americans, Australians, Britons, Japanese and West Germans.

No one ever claimed responsibility.

The report yesterday included a transcript of cockpit recordings. As the plane approached Singapore, the pilot, Captain G. K. Ganjoor, told the hijacker that the crew "were not going to do anything funny." The hijacker was heard to say, "You bluff us . . ."

After discussion about the altimeter setting, a single shot rang out followed by a low groan. Ganjoor then pleaded "No, please don't."

A second shot followed and after a third shot, the captain said, "Please, no. Oh." Then his voice faded away.

"For a reason or reasons which may never be established, the hijackers suddenly incapacitated the crew as the aircraft descended for a landing at Singapore," the report said.