Iranian protesters have stormed two British diplomatic compounds in Tehran in response to Britain's new economic sanctions against Iran.

Protesters Tuesday broke windows, scattered documents and pulled down a British flag at the embassy in central Tehran. They also looted a portrait of Britain's Queen Elizabeth. Outside, protesters chanted “Death to Britain” and set fire to a diplomatic vehicle.

Iranian media reported that Iranian police have secured the release of six embassy staff members who were surrounded by protesters at another diplomatic compound in north Tehran. The compound is used by the embassy to house students and British resident employees.

The protesters are still inside this diplomatic compound, and Iranian media say demonstrators have re-entered the British embassy despite police chasing them out earlier. State media say protesters are refusing to leave until police release those arrested when the demonstrators first attacked the embassy.

The British Foreign Office in London expressed outrage and urged Iranian authorities to act with “utmost urgency” to protect Britain's diplomatic compounds as mandated under international law. It encouraged British nationals in Iran to keep a low profile and stay indoors.

France and the United States strongly condemned the attacks.

Last week, Britain cut business transactions with all banks in Iran, including Iran's Central Bank, as part of coordinated sanctions with the U.S. and Canada.

The move was in response to Iran's suspected program to develop nuclear weapons. It was the first time Britain has cut ties with the entire banking sector of a country.

The new sanctions followed a report by the U.N. atomic energy agency strongly suggesting that Iran is researching nuclear weapons. Tehran says its nuclear activities are for civilian purposes.

On Sunday, Iran's parliament passed a bill to reduce diplomatic and economic ties with Britain.

The bill pushes the British ambassador out within two weeks, leaving Britain's embassy to be run by a charge d'affaires. Economic relations with London will also be reduced to a minimum.