British Foreign Secretary David Miliband Sunday said Iran's arrest of nine Tehran embassy staffers is "unacceptable" and demanded their release.

"This is harassment and intimidation of a kind that is quite unacceptable," Miliband told reporters while attending an international security conference on the Greek island of Corfu, The Times of London reported. "We want to see (them) released unharmed."

Iranian authorities said eight British embassy staff members were arrested Sunday for allegedly interfering in Iran's internal affairs. Iranian Parliament Member Parviz Sarvari told Iran's semi-official Fars News Agency, "The nation's tolerance for Britain's hidden and apparent policy of interference is over."

Miliband said a total of nine employees had been detained, but added some had since been released.

The foreign secretary said Britain has lodged a strong protest with Iranian authorities and indicated he would discuss the issue with European Union ministers in Corfu. The Times reported the minister had already been set to discuss post-election situation violence in Iran.

Miliband reportedly warned any further moves against Britain's embassy by Iran would be met by a coordinated EU response.