Iran seizes 15 Britons on patrol in Persian Gulf

The episode quickly added to tensions between the West and Iran over its nuclear program and its possible role in aiding insurgents in Iraq. The foreign secretary, Margaret Beckett, told reporters that she was "extremely disturbed" and had demanded an explanation from the Iranian ambassador to Britain.

The meeting between the ambassador, Rasoul Movahedian, and Permanent Under Secretary Sir Peter Ricketts of the Foreign and Commonwealth Office was "brisk but polite," a spokeswoman said.

"Sir Peter Ricketts demanded the safe return of our personnel and equipment, and emphasized the incident happened in Iraqi territorial waters," the spokeswoman said. "The Iranian ambassador undertook to relay our points to Tehran immediately."

In a statement, the Defense Ministry said the group — eight sailors and seven marines — had been conducting "routine boarding operations of merchant shipping in Iraqi territorial waters." They had just finished inspecting a merchant vessel for evidence of smuggling "when they and their two boats were surrounded and escorted by Iranian vessels into Iranian territorial waters," the ministry said.

A spokeswoman said the capture was believed to have been carried out by "Iranian sailors belonging to the Iranian Revolutionary Guard Corps Navy."

In Tehran, state television quoted an unnamed Foreign Ministry official as saying that the Britons were guilty of "blatant aggression into Iranian territorial waters."

"This is not the first time that British military personnel during the occupation of Iraq have entered illegally into Iran's territorial waters," the state TV quoted the official as saying, according to the Press Association, the British news agency.

Even before this latest events, relations between Iran and the West were particularly fraught. Iran has refused to end its nuclear program — which Western powers fear it could use to develop nuclear weapons — and has been accused of helping to finance and equip Shiite militias in Iraq.

The Britons were based on the frigate Cornwall, part of a multinational force that patrols in the northern Persian Gulf, just below the mouth of the disputed Shatt al Arab, a waterway between Iran and Iraq. Royal Navy Commodore Nick Lambert, commander of the naval force, told reporters that contact with the sailors was lost after they had searched the merchant boat, but that personnel in a helicopter overhead had seen the seizures.

"We know our helicopter reported that they saw the boats being moved up the Shatt al Arab waterway towards an Iranian base up there, and we know that there was no fighting, there was no engagement, no weapons or anything like that," Commodore Lambert said. "It was entirely peaceful, and we've been assured from the scant communications that we've had from the Iranians at a tactical level that the 15 people are safely in their hands.

"Everything I've seen from the report of the situation suggested that they reacted in impeccable fashion, totally professional, entirely in line with the rules of engagement and the direction that I have given them."

In an interview with the BBC, Commodore Lambert said that he hoped the episode was the result of a "simple misunderstanding," and that he had no doubt that the British forces, on two rigid inflatable boats, were in Iraqi territorial waters.

Ian Pannell, a BBC News correspondent on the Cornwall, reported that the confrontation took place just after the British sailors had boarded a dhow for inspection.

"While they were on board, a number of Iranian boats approached the waters in which they were operating — the Royal Navy are insistent that they were operating in Iraqi waters and not Iranian waters — and essentially captured the Royal Navy and Royal Marine personnel at gunpoint," Mr. Pannell said.

A spokeswoman for the Defense Ministry said she could not confirm that the sailors and marines had been threatened with weapons, only that no shots had been fired. The New York Times