The crew is reported to be safe, but the tanker's engine room is said to be damaged. Any impact on the environment is still unclear.
Reports of the incident came just after midnight on Tuesday, Swedish time. Just hours earlier, a separate attack on another tanker occurred, this time in the Red Sea west of Saudi Arabia.
The latest attack comes close to Oman's foreign minister's visit to Iran on Tuesday, where he is travelling to discuss the disputed Strait of Hormuz.
Maritime traffic in both the Red Sea and the Persian Gulf has been affected by the war in Iran, including when Tehran attacked what it describes as pro-US targets in the region. The Strait of Hormuz, a vital waterway for global oil trade and the passage connecting the Persian Gulf with the Gulf of Oman, has been the subject of alleged blockades in rounds by both the US and Iran.
