Eight British military personnel were today arrested by Iran after it discovered three naval vessels in its territorial waters, according to reports.
Satellite channel al-Alam said the Iranian navy confirmed it had seized men, boats, maps and weapons this morning close to Iraq and was attempting to find the purpose of their incursion. The Ministry of Defence said it was investigating the reports.
British small boat patrols regularly run along the Shatt al-Arab waterway, where the vessels were seized on Iraq and Iran's watery border, to prevent militant incursions and the smuggling out of oil from southern Iraq.
"We are assisting the Iraqi water police there so it may be one of those vessels," an MoD spokesman told the Associated Press on condition of anonymity. A later statement said British forces in southern Iraq had lost contact this morning with a patrol of three small craft.
Formed by the confluence of the Tigris and Euphrates rivers, the Shatt al-Arab connects Basra to the Gulf but has long been a source of contention between the two countries on its banks. The end of the Iran-Iraq war in 1988, in part fought over the waterway, saw a return to the pre-war status of a river spilt down the middle.
The Iraqi portion is at present under the control of the British occupying forces in the south of the country.
Britain enjoys better relations with Iran than its US coalition partners in Iraq but the reports come against the backdrop of shifting diplomacy with Tehran.
While Britain has pursued a policy of "constructive engagement" and been at the forefront of European Union efforts to negotiate with Iran over its nuclear programme, relations soured in recent days after Britain, Germany and France drafted a resolution at the International Atomic Energy Agency condemning its delaying tactics.
Tehran accused the three of caving into American pressure. Meanwhile, it today issued an angry rejection of EU criticism of its human rights record. A foreign ministry spokesman said the 25-nation union had much to learn from the Islamic Republic about respecting rights.
Like the nuclear negotiations, the two-year talks between the EU and Iran on human rights and other issues such as the Middle East peace process are an attempt to engage with Tehran in return for a lucrative trade and cooperation agreement.
The Foreign Office said British diplomats had been in contact with the Iranian government but it was still unclear what had happened.
A statement said: "The Foreign Office is liaising with the Iranian government to establish whether the detained personnel are indeed the Royal Navy boat crews, and to determine the circumstances under which they have apparently been detained."