The Malaysian coast guard shot dead a Vietnamese fisherman whose boat tried to ram a patrol vessel in the South China Sea, an official said Monday.

The incident took place inside Malaysian waters, where local fisherman have complained in the past about Vietnamese fishing boats that damage their nets.

Coast guard chief Mohamad Zubil Mat Som told AFP that two Vietnamese fishing boats had entered Malaysian waters some 80 nautical miles from Tok Bali, off the northeastern state of Kelantan late Sunday.

"The coastguard crew had earlier fired warning shots in the air but after they rammed and threw a bottle of petrol, my men had no choice but to open fire in self defence," he said.

Zubil alleged the Vietnamese crew had thrown petrol and a tyre to try and set fire to the coast guard boat, which was damaged by the "aggressive ramming".

One Vietnamese fisherman suffered gunshot wounds and was pronounced dead after he was brought to shore.

Malaysian authorities alleged Vietnamese fishermen tried to ram and set fire to a coast guard vessel in Malaysian waters
Malaysian authorities alleged Vietnamese fishermen tried to ram and set fire to a coast guard vessel in Malaysian waters AFP / MANAN VATSYAYANA

"We are saddened by this deadly incident. But I can guarantee... my men took this action to protect their lives and to protect our national sovereignty," Zubil added.

The Malaysian Maritime Enforcement Agency in a statement issued later Monday said there were 20 fishermen in the two boats, including the fatality.

The rest were also brought to shore and are under investigation for attempted murder and other offences including illegal fishing and illegal entry.

Parts of the South China Sea are subject to rival claims by Brunei, Malaysia, the Philippines, Taiwan and Vietnam, while Beijing claims the entire waterway.

The rival claims to the sea, which straddles vital shipping lanes and covers rich fishing grounds, makes it a potential flashpoint for conflict.

China and the Association of Southeast Asian Nations -- which includes four claimants -- are currently in talks for a code of conduct in the area.

In February, Kuala Lumpur sought to secure a deal with Hanoi to end alleged intrusions into Malaysian waters by Vietnamese vessels.

China Coast Guard