The 15 British sailors seized Friday in Iraqi territorial waters were taken by the Iranian Revolutionary Guards navy, a radical force that operates independently from the regular Iranian Navy, a U.S. official said.
Cmdr. Kevin Aandahl of the U.S. Navy's Fifth Fleet in Bahrain also said no shots were fired during incident and that the British sailors appeared unhurt.
Aandahl said the seizure of the British vessels, a pair of rigid inflatable boats known as RIBs, took place in long-disputed waters just outside of the mouth of the Shatt al-Arab waterway that divides Iraq from Iran.
A 1975 treaty gave the waters to Iraq and U.S. and British ships commonly operate there, but Aandahl said Iran disputes Iraq's jurisdiction over the waters, reports AP.
"It's been in dispute for some time," Aandahl said. "We've been operating there for a couple of years and we know the lines very well. This was a compliant boarding, this happens routinely. What's out of the ordinary is the Iranian response."