Authorities in Malaysia have detained a Singapore-owned tanker suspected of spilling oil off the south coast which has forced scores of fishermen to lay down their nets, a state official said today.

"We have detained a Singapore-owned ship and its crew. The chemistry department is doing a matching test to find if the oil in the water is the same as in the tanker," said Freddie Long, a Johor state executive councillor.

Long said the tanker was detained on Saturday and a clean-up was expected to begin Wednesday once equipment is deployed. The ship is being held in Pasir Gudang port, said Long, who is in charge of environmental issues in the state.

The busy shipping route was hit on Thursday by a five-kilometre-long slick which left beaches in Johor covered with tar balls and harbours full of black, oily water.

Irresponsible act

Some 200 fishermen at Pengerang on the southernmost tip of Malaysia have not been out to sea since Friday because they fear the oil slick will damage their nets.

They have criticised local authorities for not carrying out an immediate clean-up and said each boat operator was suffering daily losses of up to RM1,000.

Describing the incident as "an irresponsible act," Long said: "The people involved do not care for the environment. It is disgusting."

He urged courts to hand down tough penalties on polluters.

"I am warning the shipping industry. Stop tanker-cleaning activity. It has a serious impact on the livelihood of our local fishermen," Long said.

Abu Bakar Mohamad, president of the Fishermen's Association of Pengerang, said Monday that some 200 fishermen had been affected by the spill.