Britain on Wednesday expelled all Iranian diplomats from the country and shut its embassy in Tehran after it was attacked by an angry mob a day earlier.

Britain's Foreign Secretary William Hague announced the immediate closure of the Iranian embassy in London and gave Iran's diplomatic staff 48 hours to leave the United Kingdom.

Hague told lawmakers that although London's response is not an indication it is severing ties with Iran, the action reduces relations with Iran to the “lowest level consistent with the maintenance of diplomatic relations.”

He said that “if any country makes it impossible for us to operate on their soil they cannot expect to have a functioning embassy here.”

Iran expressed regret over the incident, but Hague said that was not good enough. He said London holds the Iranian government responsible for its failure to take adequate measures to protect the British embassy as it is required to do. He added that “clearly there will be other, further, and serious consequences.”

The attack came two days after the Iranian parliament voted to downgrade diplomatic relations with London following Britain's decision to strengthen sanctions against Iran by cutting all links with its banks.

Hundreds of students gathered Tuesday outside the British embassy in Tehran, chanting “Death to Britain.” Several protesters scaled the fence before ransacking the compound. Embassy staff was forced to flee through a back door.

The United States and Canada also tightened sanctions in response to Iran's pursuit of a nuclear program that U.N. experts say appears intended to build weapons. Iran says its nuclear program is peaceful.

Iranian parliament speaker Ali Larijani said Wednesday that Iranian police tried to maintain calm during the assaults in Tehran. He defended the attackers, saying the anger was the outpouring of several decades of exploitative actions by England in Iran, adding the protests reflected ongoing Iranian discontent with Britain.

The attacks drew more international criticism Wednesday.

U.N. Secretary-General Ban Ki-moon's office said he expressed shock and outrage as he met with a British official during an aid conference in South Korea.

U.S. President Barack Obama said he was “disturbed” by the attack, while Secretary of State Hillary Clinton strongly condemned the assault as an “affront not only to the British people but also to the international community.”

China's foreign ministry said the assault was “contrary” to international law and norms and should be dealt with “appropriately.” It was a rare Chinese criticism of Iran, a key supplier of energy to the Chinese economy.

France and Germany recalled their ambassadors to Iran for consultations, while Norway has closed its diplomatic mission in Tehran.

British media compared Tuesday's scenes to the storming of the U.S. embassy in Tehran in 1979, when militants held 52 Americans hostage for 444 days.