A tanker carrying 58,000 tonnes of naphtha was still burning, nearly 24 hours after a collision with a cargo ship in the Strait of Malacca, and had started to leak fuel, Malaysian officials said.

Officials feared the possibility of a spill of naphtha, saying firemen were cooling the ship's storage tank to prevent an explosion.

The search continued for nine of the tanker's 25-member crew. The others have been rescued.

Oil traders said the Cargill-chartered tanker, Formosaproduct Brick, was shipping the cargo of naphtha, a petrochemical feedstock, from the United Arab Emirates to Daesan and Yosu in South Korea.

The origin of the naphtha was probably the Abu Dhabi National Oil Co (ADNOC), with which US trader Cargill has a term contract to lift around 100,000 tonnes for an unspecified period, traders added.

The police chief of Port Dickson in central Malaysia told Reuters that the Liberian-registered ship was listing but there was no immediate danger that it would sink.

"Our biggest concern now is the possibility that the cargo could spill," said Mazlan Othman.

A spokeswoman from the Malaysia Maritime Enforcement Agency (MMEA) said the vessel was drifting and still ablaze, nearly 24 hours after the collision with the Ostede Max, a British- registered bulk carrier.

"The shipping lanes are not affected now because we pulled the tanker away," she said.

"There is still no word about the nine crew members."

Cargo bound for South Korea

Traders said the naphtha was destined to be supplied to South Korean end users - Honam Petrochemical, LG Chem and Yeochun Naphtha Cracking Centre (YNCC).

"The barrels were meant to arrive in South Korea in second-half August, but I doubt there will be any major impact. Inventory is not that low (in South Korea)," said a Northeast Asian trader.

"Additionally, there are still some September cargoes that traders had not sold."

Market sentiment was edgy following the collision, sending crack spreads - premiums or losses from refining Brent crude oil into naphtha - up by $US10.67 to $US108.40 a barrel.

But this was still lower than August 11, when cracks hit a near six-month high at $US114.85 a tonne, as unexpected spot exports from Saudi Arabia and China helped to plug most of the void left by a fall exports from Europe.

Asian naphtha supplies were tight after Europe choked off exports due to refinery run cuts and strong demand for the light fuels for petrochemical and gasoline production.

Most petrochemical feedstock buyers have completed their September purchases, and are looking to replenish first-half October stocks.

"As far as we know, Cargill has not indicated what they will do next," another trader said.

The collision occurred in international waters in the Malacca Straits bordering Malaysia and Indonesia, another MMEA official said, adding that the tanker was towed 33 km offshore from Port Dickson.

The MMEA spokeswoman earlier said the cargo ship was empty when it sailed from Port Dickson for Singapore at the time of the collision and the slightly damaged bulk carrier had been directed to return to the west coast Malaysian port for investigations.