U.S. President Barack Obama on Tuesday called on Iran to take to task those responsible for storming the British embassy in Tehran, saying the incident was unacceptable.

"It's important to just note that all of us, I think, are deeply disturbed by the crashing of the English embassy, the embassy of the United Kingdom in Iran," Obama told reporters at the White House before starting talks with visiting Dutch Prime Minister Mark Rutte.

"That kind of behavior is not acceptable, and I strongly urge the Iranian government to hold those who are responsible to task," the president said.

Thousands of angry Iranians staged a protest before the British embassy in central Tehran on Tuesday, and some of them broke into the compound.

And in front of the British Council compound in northern Tehran, some 300 students staged another protest and about 100 of them forced their way into the building.

British flags at both compounds were dragged down by the protesters and replaced with Iranian national flags.

"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," Obama remarked. " So obviously we're deeply concerned about that situation and we expect to see some sort of definitive action some time very quickly."

He said the Iranian government has a responsibility to protect diplomatic outposts, calling it "a basic international obligation that all countries need to observe."

The incidents in Tehran came one day after Iran's highest legislative body, the Guardian Council of the Constitution, unanimously approved reducing the diplomatic ties with Britain in response to its "hostile" policy against Iran.

In a coordinated move with the U.S. and Canada last week to impose new sanctions on Iran, Britain severed all links with Iranian banks in the wake of a report on Nov. 8 by the International Atomic Energy Agency which pointed to Tehran's attempt to acquire nuclear weapons.

After a summit meeting in Washington on Monday, U.S. President Barack Obama, European Council President Herman Van Rompuy and European Commission President Jose Manuel Barroso said that they were considering "additional measures" on Iran, citing its continued failure to abide by its international obligations.