A third of global crude oil shipments pass through the Malacca Strait
Singapore has learned that an unnamed group may be planning to attack oil tankers in the Malacca Strait, one of the world's busiest shipping lanes.
"The terrorists' intent is probably to achieve widespread publicity and showcase that they remain a viable group," the country's navy warned.
Other large vessels with dangerous cargoes were also at risk, it said.
The navy recommended ships strengthen their onboard security measures, remain vigilant and report unusual incidents.
Past cases of successful attacks on tankers were carried out using small vessels such as dinghies, speedboats and fishing boats, which are common in the Malacca Strait, the Navy advisory said.
About 33% of global seaborne crude oil shipments pass through the 965km (600-mile) channel - which is shared by Malaysia, Indonesia and Singapore.
The seaway is almost six times busier than the Suez Canal.
A Singapore Navy spokesman could not provide further details of the new threat when contacted by the Bloomberg news agency, but said it had started "operation co-ordination with our regional partners".
Malaysia's maritime enforcement agency said it was aware of the alert and was stepping up security in the shipping lane.