Foreign Secretary William Hague say UK takes 'irresponsible action extremely seriously'.
The Foreign Secretary said:
“This afternoon our two Embassy compounds in Tehran were stormed by several hundred people, putting the safety of our diplomats and their families at risk and causing extensive damage to our property.
“The United Kingdom takes this irresponsible action extremely seriously.
“It amounts to a grave breach of the Vienna Convention which requires the protection of diplomats and diplomatic premises under all circumstances.
“We hold the Iranian Government responsible for its failure to take adequate measures to protect our Embassy, as it is required to do.
“I spoke to the Iranian Foreign Minister this afternoon, to protest in the strongest terms about these events and to demand immediate steps to ensure the safety of our staff and of both Embassy compounds.
“While he said that he was sorry for what had happened and that action would be taken in response, this remains a very serious failure by the Iranian Government. The Iranian Charge d’Affaires in London has been summoned to the Foreign Office this afternoon and the Prime Minister has chaired a meeting of COBR.
“The safety of our staff is our utmost priority. On our latest information it now appears that all our staff and their dependants are accounted for. We are urgently establishing the whereabouts of our locally engaged security staff to ensure their wellbeing. All other locally engaged staff had been instructed not to attend the Embassy today because of the likelihood of demonstrations.
"We warn British nationals against all but essential travel to Iran, and we advise the small number that are in Iran to stay indoors and to await further advice.
“We have made clear to the Iranian Government that they must take immediate steps to ensure the safety of UK personnel; to ensure that property taken from the Embassy compounds is returned; and to secure the compounds with immediate effect.
“Clearly there will be other, further, and serious consequences. I will make a Statement updating Parliament on this tomorrow.”