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."