Pirates on sampans struck in the Singapore Strait again last Saturday, targeting a barge pulled by the tugboat Kim Hock Tug 9 twice in five hours.
While the pirates did not confront the crew members, they were able to escape with several pieces of scrap metal.
In an incident alert on Sunday, the Regional Cooperation Agreement on Combating Piracy and Armed Robbery against Ships in Asia's Information Sharing Centre (ReCAAP ISC) said the same barge laden with scrap metal was targeted twice in the east-bound lane of the strait.
At about 11.30am, seven pirates were spotted on the barge being towed from Singapore to Vietnam.
When another tugboat approached the barge, the pirates fled in three sampans with some scrap metal.
A few hours later, at about 4pm, seven pirates were again spotted on the same barge, and two Singapore Police Coast Guard craft were dispatched to intercept them.
But the pirates again evaded capture, escaping on their sampans with more scrap metal.
Both incidents happened about 20km apart in the waters between Singapore and Batam.
It is not known if the same group of pirates was involved in both attacks.
ReCAAP ISC said the attacks were the second and third this year, with the first being the tanker British Mariner, which was attacked on Jan 8 while in the east-bound lane.
ReCAAP ISC said it was concerned about the continued incidents, and urged greater vigilance and cooperation.
"All ships are strongly advised to exercise utmost vigilance, adopt extra precautionary measures and report all incidents immediately to the nearest coastal state," it said.
"The ReCAAP ISC recommends to the law enforcement agencies of the littoral states to further step up surveillance, increase patrols and enhance cooperation and coordination among them in order to respond promptly to incidents."
There was a sudden spike in incidents in the Singapore Strait in December last year, with a total of eight attacks by knife-wielding pirates in the east-bound lane.
Last year also saw an overall surge in piracy incidents in the strait, with 31 attacks compared with eight in 2018.
Just last week, the Republic of Singapore Navy hosted the 14th Malacca Straits Patrol Joint Coordinating Committee Meeting, which saw representatives from Indonesia, Malaysia, Singapore and Thailand discuss the recent increase in piracy incidents in the strait.
The representatives signed a revised set of standard operating procedures, pledging to strengthen information sharing and enhance mutual understanding and collaboration.