Johor has been hit by a giant oil slick believed to be the region's worst environmental disaster in recent years, a report said yesterday.

Fishermen in Pengerang, on the southernmost tip of Malaysia, on Saturday alerted the state's environment department to the five-kilometre long slick, the New Straits Times said.

Environment officials have taken samples of the oil which has affected docks and beaches in the area known for its fishing industry. However, they are yet to determine the source of the spill.

Worst ever

"The Pengerang shore has experienced oil slick cases before but this is the worst I have seen," fisherman Teo Seng Huat told the newspaper.

The report included photographs which showed a thick layer of oil on beaches and floating at sea, and black oily water surrounding boats in the harbour.

The waters off Johor's shores lie along the region's busiest shipping lanes in the South China Sea.