Aboard HMS Cornwall, Persian Gulf (CBS) - Iranian naval vessels seized 15 British sailors and marines Friday in Iraqi waters, the UK Ministry of Defense (MoD) said.

Al Alam Television, an Iranian Arabic language station confirmed the capture of the Britons.

The U.S. Navy's Fifth Fleet in Bahrain said the group were taken by the Iranian Revolutionary Guards navy, a radical force that operates independently from the regular Iranian Navy, but no shots were fired during incident and that the British sailors appeared unhurt.

Britain summoned Iran's ambassador in London to demand their release.

The British personnel from the frigate HMS Cornwall were making "routine" inspections of "merchant shipping in Iraqi territorial waters," and had finished inspecting one ship when they were accosted by Iranian vessels, the ministry said in a statement.

"We are urgently pursuing this matter with the Iranian authorities at the highest level," the ministry said, adding that "the Iranian ambassador has been summoned to the Foreign Office."

"The British government is demanding the immediate and safe return of our people and equipment," it said.

"I've got 15 sailors and marines who have been arrested by the Iranians and my immediate concern is their safety," the Cornwall's commander, Commodore Nick Lambert said in an interview aboard his vessel .

"There is absolutely no doubt in my mind that we were in Iraqi waters. Equally the Iranians will claim that they were in Iranian waters. The extent and the definition of territorial waters is very complicated," he added.

"Big Iranian boats came and took the two (British) boats with their crews to the Iranian waters," a local fisherman said.

The Royal Navy sailors were reportedly assigned to a naval task force whose mission is to protect the Iraqi oil terminals in the south of the nation along the Shatt al-Arab waterway, which also serves as a border between Iraq and Iran, and maintain security in Iraqi waters under the U.N. mandate of the Security Council resolutions on Iraq.

In June 2004, six British marines and two sailors were seized by Iran in the Shatt al-Arab.

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

They were released unharmed after three days.