The oil producing countries around the Gulf, including Kuwait, Saudi Arabia, Iraq and Iran, are crucial for supplying the world oil market. Most of their exports must travel through the Strait of Hormuz.
The Bahrain-based US Navy Fifth Fleet said it was assisting the tankers after receiving distress calls following "reported attacks". The United Kingdom Maritime Trade Operations, part of the Royal Navy, said it was investigating.
``Often it is a brutal reminder that what we do is dangerous work in an unforgiving environment, requiring honed skills and constant vigilance,'' Sawyer said. ``And even with those, bad things can happen.''