Britain on Tuesday said it was "outraged" by the storming and vandalising of its embassy in Tehran by protesters, asking the Iranian Government to act urgently to bring the situation under control.
Condemning the incursion by demonstrators into the embassy premises in Tehran, the Foreign Office said a significant number of demonstrators entered into the embassy premises and vandalised the property.
"We are outraged by this. It is utterly unacceptable and we condemn it," a Foreign Office spokesperson said.
He said the situation was still fluid and details were still emerging.
"Under international law , including the Vienna Convention, the Iranian Government have a clear duty to protect diplomats and Embassies in their country and expect them to act urgently to bring the situation under control and ensure the safety of our staff and security of our property," the spokesman added.
According to reports from Tehran, over 20 Iranian protesters stormed the British embassy, removing the mission's flag and ransacking offices.
The protesters threw stones at embassy windows, breaking them, and one demonstrator was seen climbing the wall with a looted portrait of Britain's Queen Elizabeth II.
The attack comes amid heightened tensions following Iran's decision to pass a law to expel London's ambassador to Tehran in retaliation for new British sanctions that cut off all ties with Iran's financial sector. The sanctions are aimed at putting more pressure on Iran to halt its controversial nuclear programme.