BBC News with Zoe Diamond

The British Prime Minister David Cameron has said Iran will face serious consequences after hundreds of protesters stormed two British diplomatic compounds in Tehran. Mr Cameron described the attacks as "outrageous and indefensible", sentiments echoed by the Foreign Secretary William Hague.

"The United Kingdom takes this irresponsible action extremely seriously. It amounts to a grave breachof the Vienna Convention. We hold the Iranian government responsible for its failure to take adequate measures to protect our embassy as it is required to do." During the storming, offices were smashed and flags torn down in the attacks, which followed a demonstration against sanctions imposed on Iran over its nuclear programme. The Iranian foreign ministry has expressed regret for what it described as the unacceptable behaviour of a small group of protesters.