LONDON, March 23 (Xinhua) -- British Foreign Secretary Margaret Beckett said on Friday that Britain demanded "immediate and safe return" of 15 British navy personnel detained by Iranian forces.

    "We have sought a full explanation of what happened and we are leaving them in no doubt that we want the immediate and safe return of our personnel and their equipment," she said after summoning the Iranian ambassador to London Rasoul Movahedian on Friday afternoon.

    "The meeting with the Iranian ambassador was brisk but polite. But he was left in no doubt that we want them back," she added.

    Iranian naval vessels detained 15 British soldiers at approximately 10:30 a.m. Iraqi time (0730 GMT) on Friday, when they were engaged in routine boarding operations of merchant shipping in Iraqi territorial waters, in support of UN Security Council Resolution 1723 and the Iraqi government.

    "The UK 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," said the MoD.

    Britain is urgently pursuing this matter with the Iranian authorities at the highest level.

    Sky News said the captives, from the Type 22 frigate HMS Cornwall, were seized in the controversial Shatt Al Arab waterway, which divides Iraq form Iraq. The British Royal Navy insisted that they were operating in Iraqi waters and not Iranian territorial waters.

    It is reported that the operation was part of a crackdown on smugglers.

    However, Iran said it detained 15 British servicemen because they had crossed into Iranian waters, Sky News said, citing Iran state television.

    An Iranian Foreign Ministry official was quoted as saying they were "detained by Iran's border authorities for further investigation ... of the blatant aggression into Iranian territorial waters."

    According to BBC, this is not the first time that British troops have been seized by Iranian forces in the troubled waters between Iran and Iraq. In 2004, Iran detained eight British servicemen for three days after they allegedly strayed over the maritime border.