British Foreign Secretary David Miliband arrives at 10 Downing Street in central London on June 29, 2009. Britain confirmed Monday that five of the nine British embassy staff arrested in Tehran had been released but said the continuing detention of four people was "unacceptable and unjustifiable". EU nations vowed Sunday to respond to any harassment of diplomats in Iran with a "strong and collective response," Britain's foreign secretary said after the arrest of British embassy staff.