Britain and the United States have condemned Iran for failing to stop the protesters who stormed the British Embassy in Tehran Tuesday.
Now Britain is withdrawing some embassy staff from Iran. It's also vowing to expel all Iranian officials from the United Kingdom.
"Ensuring the safety of our staff and their families is our immediate priority," London's Foreign Office said in a statement.
On Tuesday, Iranian rioters surged past police and attacked the British and U.S. diplomatic compounds with gas bombs and rocks.
Outside the embassy, university and Muslim seminary students burned homemade British, American, and Israeli flags.
The assault on the embassy was reminiscent of the historic takeover of the U.S. Embassy in 1979.
British Prime Minister David Cameron called Tuesday's attack "outrageous and indefensible."
"The Iranian government must recognize that there will be serious consequences for failing to protect our staff," Cameron said after a meeting with a security committee.
President Obama expressed similar sentiments, saying the Iranian government showed its true colors by not stopping the rioters in time.
"They have a responsibility to protect diplomatic outposts," the president said. "That is a basic international obligation that all countries need to observe."
"And for rioters, essentially, to 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," he added.
Tuesday's assault came days after England passed new restrictions meant to punish Iran for its nuclear program.