BASRA, Iraq (Reuters) - Iranian forces seized 15 British Royal Navy personnel who had searched a merchant ship on Friday, the Ministry of Defence said, triggering a diplomatic crisis at a time of heightened tensions over Tehran's nuclear ambitions.
The ministry said the incident took place in Iraqi waters, where it routinely boards merchant vessels with U.N. permission to search them. The Foreign Office summoned Iran's ambassador and demanded the immediate, safe release of the personnel.
The incident took place a day after Iran launched a week of naval war games along its coast, including the narrow northern reaches of the Gulf which control access to the vast oil reserves of Iraq, Iran and Kuwait.
The United Nations Security Council is expected to vote on Saturday on a resolution to impose new sanctions against Iran over its refusal to halt uranium enrichment.
Oil prices rose by about a percent to above $62 a barrel after the incident.
"...This morning 15 British naval personnel, engaged in routine boarding operations of merchant shipping in Iraqi territorial waters ... were seized by Iranian naval vessels," the Defence Ministry said in a statement.
"The boarding party had completed a successful inspection of a merchant ship when they and their two boats were surrounded and escorted by Iranian vessels into Iranian territorial waters," it said.
Iranian officials could not immediately be reached for comment. The embassy in London was closed for a holiday.
"Hopefully there has been a mistake that has been made and we will see early clarification and an early release of my people," Commodore Nick Lambert, commander of the British fleet in the area, said in a television interview aboard HMS Cornwall.
"There was no fighting, no engagement of weapons, anything like that, it was entirely peaceful. We have been assured from the scant communication we have had with the Iranians at a tactical level that the 15 people are safely in their hands."
An Iraqi fisherman in Basra told Reuters he had seen the incident in the Shatt al-Arab waterway that marks the southern stretch of Iraq's border with Iran. There was no sign of any violence, said the fisherman, who asked not to be named.
He said Western military personnel on two small boats had boarded a ship the Siban area of the waterway, near the al-Faw peninsula that leads into the northern Gulf. At least two Iranian vessels appeared on the scene and detained them.
British Royal Navy personnel include both sailors and marines, who make up boarding parties for ship searches as part of a mission that also includes U.S. and Australian forces. Washington said no U.S. military personnel were involved.
The incident was similar to one in 2004 in which eight British servicemen spent three nights in the hands of Iranian Revolutionary Guards before being released unharmed.
In that incident, the Iranians accused them of crossing into Iranian waters, which Britain disputed.
Unlike the United States, Britain has diplomatic relations with Iran. But London backs Washington's strong calls for sanctions against Iran unless it abandons nuclear plans which the Western countries believe are aimed at producing weapons.
The two countries also accuse Iran of fomenting violence in Iraq. Iran insists its nuclear plans are peaceful and denies it supports militia in Iraq.