Maritime security company Ambrey has warned vessels to take precautions in the Singapore Strait after a second boarding incident in less than two weeks.

Four armed men got onto the deck of an unnamed Liberia-flagged bulk carrier at 20:00 hours local time on Tuesday while the ship was transiting eastbound through the Philip Channel in the strait.

The vessel was 12 nautical miles (22 km) north-west of Pulau Terung, Indonesia, at the time.

The gang was armed with knives, Ambrey said.

The bulker continued its journey to Singapore.

Its freeboard was 6.35 metres.

Ambrey said: “Crews transiting the Singapore Strait with freeboards lower than 10 metres are advised they are at heightened risk.

“Crews should lock down access to the accommodation block and ship’s stores. It is recommended to carry out partnered deck patrols. Do not confront criminals,” the company added.

The incident came 11 days after another boarding of a Liberia-flagged bulker by five robbers in the Philip Channel, north-west of Kapalajernih Island, Indonesia.

The suspects were reportedly armed with a “gun-like” object, Ambrey reported.

During the incident, the vessel was underway at 7.9 knots, with an estimated freeboard of 5.75 metres, after an initial report that the figure was closer to 13 metres.

Ambrey had carried out further investigations and rechecked the vessel’s estimated freeboard upon arrival in Singapore.

The revised height above the water is well within the “established capability” of criminals operating in the Singapore Strait, the company said.

The bulker was able to continue its journey.