Malaysia’s maritime agency says it has limited ability to stop Iranian-linked tankers from transferring oil to other ships off its coast, allowing Iran to skirt sanctions and drawing growing criticism.

United Against Nuclear Iran, a U.S.-based advocacy group, says there have been 42 ship-to-ship transfers of Iranian oil conducted in the waters about 70 kilometers (45 miles) off Malaysia’s southern Johor state, since Feb. 28, when the U.S. and Israel attacked Iran, starting a war in the Middle East. UANI used satellite imagery to observe the operations.

The ship-to-ship transfers have been criticized by shipping industry organizations and UANI, which has accused Malaysia of being too lax in enforcement efforts.

Malaysian Maritime Enforcement Agency Director-General Mohamad Rosli Abdullah says the transfers are often done in international waters where Malaysia has no jurisdiction, and that these vessels, known as “shadow fleet,” are also often able to evade detection by switching off tracking systems, using…