Britain led a chorus of international outrage on Tuesday over the storming of its embassy in Tehran by protestors, with even Iranian ally Russia joining condemnation of the raid.
"The attack on the British Embassy in Tehran today was outrageous and indefensible," Prime Minister David Cameron said in a statement. "The failure of the Iranian government to defend British staff and property was a disgrace... We hold the Iranian government responsible."
"The Iranian government must recognise that there will be serious consequences for failing to protect our staff," vowed Cameron, adding that "we will consider what these measures should be in the coming days."
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Protestors stormed Britain's embassy and another diplomatic compound in Tehran, trashing offices and stealing documents in attacks that dramatically escalated the West's standoff with Iran over its nuclear programme and sparked international alarm.
The protests came after Britain last week said it would cut off all relations with Iran's financial sector as part of a raft of sanctions coordinated with the United States and Canada.
IRAN REGRETS STORMING
Iran's foreign ministry later expressed regret over the "unacceptable" storming, adding that "the relevant authorities have been asked to take the necessary measures and look into this issue immediately."
The foreign ministry issued a statement expressing "regret for certain unacceptable behaviour by a small number of protesters".
It emphasised what it said was the Iranian government's commitment "to protecting the rights of diplomats and diplomatic locations".
Tehran police chief General Hossein Sajadinia said several protesters had been arrested and would face the courts.
US 'DISTURBED'
In Washington US President Barack Obama said he was "deeply disturbed" by the attack.
"That kind of behaviour is not acceptable, and I strongly urge the Iranian government to hold those who are responsible to task," he told reporters at the White House.
"And for rioters to basically be able to overrun the embassy and set it on fire is an indication that the Iranian government is not taking its international obligations seriously.
"So obviously we're deeply concerned about that situation and expect some sort of definitive action some time very quickly," he added.
RUSSIANS CONCERNED
Close Iran ally Russia also slammed the attacks as "unacceptable and deserving condemnation," according to a foreign ministry statement.
Moscow said it hoped "the Iranian authorities undertake necessary measures to immediately restore order, investigate what happened, and prevent a repetition of such incidents."
It added that the raid "was conducted in contravention of generally accepted norms of international law" and expressed support for the British diplomats.
Moscow is Tehran's closest ally among the major world powers, conducting regular consultations with Iranian officials even as they face growing diplomatic isolation from the West.
At the United Nations headquarters in New York, the Security Council warned Iran that it must protect diplomatic personnel, though it made no threat of action against Tehran.
"The members of the Security Council condemned in the strongest terms the attacks" against the British embassy in Tehran, said a statement agreed by the 15-nation body that has passed four rounds of sanctions against Iran over its nuclear programme.
Highlighting the Vienna conventions which protect diplomats, the Council "called on the Iranian authorities to protect diplomatic and consular property and personnel, and to respect fully their international obligations in this regard."
In Brussels, EU foreign policy chief Catherine Ashton said in a statement of her "extreme concern" over the incident and called on Tehran "immediately to fulfill its international obligations... to protect diplomats and embassies."
French Foreign Minister Alain Juppe saw as another example of Iran's attitude toward international law.
"Once more, the Iranian regime has shown what little consideration it has for international law. France denounces this flagrant and outrageous violation of the Vienna Convention" on diplomatic relations, Juppe said in a statement.
In Berlin, Germany summoned the Iranian ambassador.
"We condemn the storming of the British embassy in Iran, in which the German school there was also damaged, in the strongest terms. This storming is in violation of international law, it is in no way acceptable," Foreign Minister Guido Westerwelle told reporters.
And in Madrid, the Spanish foreign ministry strongly condemned the attack, adding that it "rejects the insufficient response that the Iranian authorities have taken in response to these grave acts."
