A Singapore-registered container ship leaked 150 metric tonnes of fuel oil after it ran aground early on Thursday on the way to China, the Maritime and Port Authority (MPA) of Singapore said.
Six anti-pollution craft were deployed to clean up the spill, which led to three oil patches about 300 metres long and 100 metres wide, the MPA said in a statement.
The 40,077-tonne MV APL Emerald, which ran aground 1.3 kilometres south of the Horsburgh lighthouse in Singapore waters, had one of its water ballast tanks and four fuel oil tanks damaged, the MPA said.
"The shipmaster estimated that about 150 metric tonnes of fuel oil had leaked into the sea," the MPA said.
"There was no report of any injury to the crew. The vessel is in stable condition."
The MPA said none of the oil had reached mainland Singapore and that port operations and ship traffic was unaffected.