The spill started early Sunday morning on a pipeline running between two islands, Bukom and Bukom Kecil, Singapore's Maritime and Port Authority of Singapore (MPA) said in a statement.

"The leak was reported to have stopped at source," the MPA said. "Shell has placed containment booms off the site of the leak and has also deployed craft equipped with dispersants to clean up the oil sighted in the vicinity of the leak."

The authority said it also dispatched equipment and a team to help clear the fuel slick, and activated drones and satellite capabilities to monitor the spill.

"Relevant government agencies have been alerted and to report any oil sightings," it said, adding there had been "no new oil sightings" as of Sunday evening.

Shell operates a major oil refinery on Bukom. The company could not immediately be reached for comment on Sunday evening.

The MPA said it has issued "navigational safety broadcasts to ask passing vessels to keep clear of the site" although "there is no impact to navigation safety".

In June, Singapore closed beaches on the resort island of Sentosa after an oil spill caused by an accident at the Pasir Panjang port between a dredger and a stationary bunker vessel.

Clean-up of the affected beaches was completed last month.