Wed Sep 26, 4:22 PM ET

YANGON - Myanmar security forces used batons, tear gas and live rounds Wednesday in a violent crackdown on mass protests against the military junta, killing at least four people including three Buddhist monks.

Up to 100,000 people defied heavy security to take to the streets of the main city Yangon, marching and shouting abuse at police despite blunt warnings from the ruling generals who are facing the most serious challenge to their rule in nearly two decades.

Two of the monks were beaten to death while another was shot when he tried to wrestle a gun away from a soldier and the weapon discharged, two senior Myanmar officials told AFP.

They said the monks were killed near Yangon's Shwedagon Pagoda, Myanmar's holiest site and a key rallying point for the clergy who have led nine days of protests which have spread across the Southeast Asian nation.

A fourth man, who was not a monk, was shot dead, a hospital source said.

The United Nations Security Council held emergency talks in New York late Wednesday to discuss the spiralling crisis, as international outrage over the violent crackdown mounted.

The UN's point man on Myanmar, special envoy Ibrahim Gambari, was to brief the closed-door meeting.

Earlier, UN Secretary General Ban Ki-moon said he was sending Gambari to the region immediately and urged the junta to "cooperate fully" with his mission.

The United States and the European Union called on authorities "to stop violence and to open a process of dialogue with pro-democracy leaders," including detained Nobel laureate Aung San Suu Kyi.

The G8 grouping of the world's eight most industrialised nations condemned the violence and warned the generals that they would be held accountable for their actions.

British Prime Minister Gordon Brown, whose country is the former colonial power, said "the whole world is now watching Burma," and French President Nicolas Sarkozy called on French businesses to freeze their investments here.

After tolerating more than a week of protests, police opened fire and baton-charged protesters who had begun to gather at the Shwedagon Pagoda in the blazing noon sunshine.

Undeterred by the show of force, some 1,000 monks soon regrouped and paraded through the streets, to the delight of thousands of onlookers.

They roared approval for the monks and shouted at security forces: "You are fools! You are fools!"

Police and troops then fired a volley of warning shots and tear gas to try to break up the march.

In a sign of the resilience and determination of the protest movement, tens of thousands of monks massed once again, marching through the main market in a protest that lasted until the early evening.

At least 100 people were injured during the day and some 200 people were arrested, as many as half of them Buddhist monks, according to witnesses and diplomats.

State television news said that one 30-year-old protester had been killed, and another two men and one woman were injured, along with 10 police.

The report said security forces had used loudspeakers to ask the crowd to disperse but that the protesters had hurled stones and sticks at them, tried to steal their weapons, and set fire to two military motorcycles.

"Because of the difficult situation, the security forces opened fire to disperse the crowd, using just a little force against the violent protesters. Because they opened fire, the protesters dispersed," it said.

The party of pro-democracy leader Aung San Suu Kyi branded the assaults on the monks -- highly revered in the devoutly Buddhist nation -- "the greatest wrong in history."

Protesters ignored a ban on public gatherings issued Tuesday along with a dusk-to-dawn curfew, as the generals who have turned Myanmar into one of the world's poorest and most isolated nations tried to keep a lid on the unrest.

Wednesday was the first time violence has been used against the recent protests, and analysts said it could be a preview for an even more severe crackdown in coming days.

There are fears of a repeat of 1988, the last time demonstrators rallied in such numbers in the streets of Myanmar, formerly known as Burma. Then, around 3,000 people were killed by the security forces.

There were sketchy reports Wednesday of huge turnouts and further clashes with police in the central city of Mandalay and in Sittwe on the western coast where 15,000 people marched.

The unrest began last month when the junta dramatically raised the price of fuel overnight, deepening the misery in this already impoverished country.

The initial protests -- rare in a nation where the military quickly crushes any show of dissent -- began with only a handful of marching demonstrators.

But after the monks joined, the movement swelled, and around 100,000 people marched in Yangon on Monday and Tuesday.