TEHRAN: Iran was bracing for pro-government student protests against the British embassy in Tehran on Tuesday as the world voiced increasing alarm at the violent crackdown on opposition demonstrators.

Hundreds of riot police armed with steel clubs and firing tear gas, many riding on motorbikes, put down an opposition rally in the capital on Monday after the Revolutionary Guards warned it would crush further protests.

Iran has singled out Britain as one of the leading instigators of what it says is foreign "meddling" in the chaos that has engulfed the country since the disputed re-election of President Mahmoud Ahmadinejad 11 days ago.

World leaders are calling for a halt to violence against opposition protesters who have staged almost daily rallies over an election that Ahmadinejad's main defeated rival Mir Hossein Mousavi has branded a fraud.

UN chief Ban Ki-moon on Monday voiced growing concern about the post-election violence and urged "an immediate stop to the arrests, threats and use of force." He appealed to the government and the opposition "to resolve peacefully their differences through dialogue and legal means." The White House bemoaned the lack of "justice" experienced by protesters in Iran, and said President Barack Obama had been moved by scenes of demonstrators braving repression, especially women.

Some European governments have begun urging nationals to avoid travel to Iran, caught up in the worst crisis since the revolution 30 years ago that is threatenening the very foundations of the Islamic republic.

Foreign media have been restricted in their reporting of the crisis, with a ban on the coverage of all unauthorised demonstrations but images of police brutality have spread worldwide via amateur video over the Internet.

In Tehran on Monday, riot police backed up by the Islamic Basij militia arrested up to 60 people in a crackdown on about 1,000 people who gathered in defiance of the Revolutionary Guards which had warned of a "decisive and revolutionary" riposte At least 17 people have been killed and many more wounded in the post-election violence, according to state media, while hundreds of protestors and prominent reformists and journalists rounded up -- even figures close to top regime figures.

Four student unions said they were planning to stage protests outside the British embassy on Tuesday in protest at London's alleged interference in the unrest.

The Fars news agency quoted student leader Esmail Tahmouressi as warning of another "November 4", the date when radical students seized the US embassy in Tehran after the 1979 revolution.

Iranian lawmakers have called for Tehran to review its often strained relations with London, while the BBC correspondent has been expelled.

Britain said it was pulling out relatives of embassy staff in Tehran and, along with Italy and Germany, warned its nationals against travelling to Iran.

The 27-member European Union on Monday rejected Iran's claims of interference as "baseless and unacceptable" but voiced deep concern about the continuing brutality and called for the crisis to be settled through "democratic dialogue and peaceful means." British Foreign Secretary David Miliband rejected charges that protesters were being "manipulated" by foreign nations and denounced what he said were Iran's efforts to turn the election into a "battle" with the outside world.

Rights watchdog Amnesty International urged Iran to "stop using Basij militia to police demonstrations", saying they have reportedly used "excessive force" against protesters.

Footage broadcast on the Internet has shown scenes of brutal violence in Tehran, with one video viewed by hundreds of thousands around the globe purportedly showing a bloodstained young woman named Neda reportedly killed when hit by a bullet in Tehran.

Mousavi, who has led the protests over his defeat in what he says was a rigged election that gave Ahmadinejad another four years in power, urged supporters to continue demonstrating but to adopt "self-restraint" to avoid more bloodshed.

And in a sign the opposition remained defiant, defeated reformist candidate Mehdi Karroubi called for a ceremony on Thursday to mourn protesters slain in demonstrations.

Election watchdog the Guardians Council acknowledged some discrepancies in the June 12 vote but insisted they would not effect the outcome, while the opposition is insisting not on a recount but a new vote.

Mousavi, Karroubi and the third defeated challenger Mohsen Rezai have listed a total of 646 irregularities in the June 12 vote.