Britain is demanding the immediate release of 15 Royal Navy sailors and marines seized Friday by Iranian naval forces in Iraqi waters in the Persian Gulf.

The detained British navy personnel were in two inflatable boats from the HMS Cornwall, pictured here in the North Arabian Gulf this month.
(British Royal Navy/Associated Press)

"We want our personnel and equipment back," said British Foreign Secretary Margaret Beckett, who immediately called in Iran's ambassador in London to the Foreign Office.

"He was left in no doubt that we want them back," Beckett said after the meeting.

Beckett said the sailors and marines were in Iraqi waters at Iraq's request and operating under the authority of the United Nations to stop smuggling.

Iran also summoned the top British diplomat in Tehran to protest the sailors' "illegal entry" into Iranian waters, Iranian state TV reported.

"This is not the first time that British military personnel during the occupation of Iraq have entered illegally into Iran's territorial waters," state TV quoted a Foreign Ministry official as saying. He was not identified by name.

Royal Navy personnel were on routine patrols of merchant shipping in Iraqi territorial waters Friday, the British Defence Ministry said.

The sailors had just completed a search of a merchant ship suspected of smuggling cars. The vessel was cleared to continue its journey.

But as the British sailors were getting onto their own vessel, they were surrounded by Iranian naval vessels and seized at gunpoint.

The British sailors were taken into Iranian waters but it is unclear where they are being held.

The ministry has issued a demand to Iranian authorities for "the immediate and safe return of our people and equipment."

"[The British government] is adamant that its sailors were in Iraqi territorial waters, not in Iranian waters," the CBC's Adrienne Arsenault said.

Sailors captured in disputed waters

The Iranian ambassador has been summoned to the foreign office in London.

Cmdr. Kevin Aandahl of the U.S. Navy's Fifth Fleet said the British crew members were intercepted by several larger patrol boats operated by Iranian sailors belonging to the Iranian Revolutionary Guard Corps Navy, a force that operates separately from the country's regular navy.

The Iranian boats normally carry bow-mounted machine guns, while the British boarding party carried only sidearms, Aandahl said. No shots were fired and there appeared to be no physical harm done to any personnel involved or their vessels, he said.

The seizure of the British vessels, a pair of rigid inflatable boats known as RIBs, took place in long-disputed waters just outside the mouth of the Shatt al-Arab waterway that divides Iraq from Iran, Aandahl said. 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.

"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."

Arsenault said it is expected that Iran will accuse the British sailors of being spies as they did during a similar incident in 2004, when eight British sailors were seized.

In that incident, however, it was accepted that they had veered into Iranian territorial waters.

They were presented blindfolded on Iranian television and admitted to entering Iranian waters illegally.

The sailors were released unharmed after three days.

With files from the Associated Press