Tehran has called on London to respond to its release of 15 UK naval personnel with a gesture of good will, indicating it wants Britain's help to free five Iranians held in Iraq and ease concerns about its nuclear programme.

"We played our part and we showed our good will," Rasoul Movahedian, Iran's ambassador to the UK, told the Financial Times, in his first interview since the crisis began. "Now it is up to the British government to proceed in a positive way."