Six marines and two navy sailors were detained for three days in Iran last week, during which they were paraded blindfold on television and forced to publicly apologise for what they called a "mistake".

Iran insisted that the boats were intercepted only after they entered Iranian waters on the Shatt al-Arab waterway that divides southern Iraq from Iran.

But British Defence Secretary Geoff Hoon made a written statement to parliament Wednesday that the men believed they were "forcibly escorted" over the maritime border by Iranian troops.

"The boats were on an entirely routine operation," British Prime Minister Tony Blair's official spokesman said Thursday. "There was no intention to go into Iranian waters."

"We still want our boats returned, not least because that would help finally to resolve what did happen because of the navigational equipment on board," he said.

Iran defended Thursday its arrest of the eight-man British Royal Navy unit, asserting that London's contention that they were forced into the Islamic republic's waters was "incorrect".

"We are surprised by the British defense minister's incorrect remarks," Iranian foreign ministry spokesman Hamid Reza Asefi said in a statement.

Britain has said that discussions over the boats were continuing with the Iranians and that the defence ministry was still looking into the incident which has threatened to derail relations between the countries.