TEHRAN, Iran (AP) -- Hard-line Iranian students stormed the British diplomatic compounds in Tehran on Tuesday, bringing down the Union Jack flag and throwing documents from windows in scenes reminiscent of the anger against Western powers after the 1979 Islamic Revolution.
The mob surged past riot police into the British Embassy compound - which they pelted with petrol bombs and stones - two days after Iran's parliament approved a bill that reduces diplomatic relations with Britain following London's support of recently upgraded Western sanctions on Tehran over its disputed nuclear program.
Less than two hours later, police appeared to regain control of the site. But the official IRNA news agency said about 300 protesters entered the British ambassador's residence in another part of the city and replaced British flags with Iranian ones. The British Foreign Office harshly denounced the melee and said Iran has a "clear duty" under international law to protect diplomats and offices.
"We are outraged by this," said the statement. "It is utterly unacceptable and we condemn it."
It said a "significant number" of protesters entered the compound and caused vandalism, but gave no other details on damage or whether diplomatic staff was inside the embassy, although the storming occurred after business hours.
The semiofficial Mehr news agency said embassy staff had left the compound before the mobs entered, but it also said those who occupied the area had taken six staff as hostages. It did not give their nationalities and the report was later removed from the website without elaboration.
The protesters broke through after clashing with anti-riot police and chanting for its takeover. "Death to England," some cried in the first significant assault of a foreign diplomatic area in Iran in years. More protesters poured into the compound as police tried to clear the site.
Smoke rose from some areas of the embassy grounds and the British flag was replaced with a banner in the name of 7th century Shiite saint, Imam Hussein.
The occupier called for the closure of the embassy calling it a "spy den" - the same phrase used after militants stormed the U.S. embassy in Tehran in 1979 and held 52 hostages for 444 days. Washington and Tehran have no diplomatic relations since then.
The rally outside the British Embassy - on a main street in Tehran downtown - included protesters carrying photographs of nuclear scientist Majid Shahriari, who was killed last year in an attack that Iran blamed on Israeli and British spy services.
Outside the embassy, students from some universities and seminaries burned British flags on fire as clashing with police.
State TV reported that another group of hard-line students gathered at the gate of British ambassador's residence in northern Tehran, at the same time.
Tensions with Britain date back to the 19th century when the Persian monarchy gave huge industrial concessions to London, which later included significant control over Iran's oil industry.
But they have become increasingly strained as the West accuses Iran of trying to develop nuclear weapons - a charge Tehran denies.
In recent years, Iran was angered by Britain's decision in 2007 honor author Salman Rushdie with a knighthood.
Rushdie went into hiding after Iran's Ayatollah Khomeini issued a 1989 fatwa, or religious edict, ordering Muslims to kill the author because his novel "The Satanic Verses" allegedly insulted Islam.
The decision shortly after Iran detained 15 British sailors and marines in March 2007 for allegedly entering the country's territorial waters in the Persian Gulf - a claim Britain denies. The 15 were released after nearly two weeks in captivity.
In 2006, angry mobs burned the Danish flag and attacked Danish and other Western embassies in Tehran in protest to the reprinting of a cartoon deemed insulting of the Prophet Muhammad in the Nordic country's newspapers.