Theft of scrap metal from barges in the Singapore Strait is raising concerns with Asian anti-piracy outfit ReCAAP.

The group said in a report Thursday that the number of incidents involving tugs and barges is on the rise, hitting 14 this year.

"Although all the 14 incidents were [petty theft] in nature as the perpetrators were not armed and the crew not harmed, the ReCAAP ISC is concerned about the increase in the number of incidents," the report read."

ReCAAP said over the last 13 years, there were a total of 228 incidents on tug boats and barges in Asia. Of those, 98 were in the Singapore Strait, three-quarters of which were robberies and the remainder theft of scrap.

The 14 incidences of the latter this year is an increase over the past four years, the group said. Usually, the thefts happen when perpetrators pull up alongside the barge and pull scrap onto their boats.

ReCAAP recommends tug crews stay on the lookout for small boats and sound the alarm when suspicious boats loiter in the vicinity of the barge. The report also recommends shortening the tow line between the tug and the barge.