The government of Myanmar began a violent crackdown today after tolerating more than a month of ever-larger protests in cities around the country, clubbing and tear- gassing protesters, firing shots into the air and arresting hundreds of the monks who are at the heart of the demonstrations.

The Reuters news agency quoted hospital and monastery sources as saying two monks and a civilian were killed and several people were wounded in the crackdown.

Despite threats and warnings by the authorities and despite the beginnings of a violent response, tens of thousands of chanting, cheering protesters flooded the streets, witnesses reported. Monks were in the lead, “like religious storm troopers,” as one foreign observer described the scene.

Though the crowds were large and energetic, they were smaller than on previous days, apparently in part because of the deployment of armed soldiers to prevent monks from leaving some of the main temples.

But it appeared that an attempt by the military to halt the protests through warnings, troop deployments and initial bursts of violence had not succeeded. Analysts said that the next steps in the crackdown might be yet more aggressive and widespread.

A foreign diplomat described “an amazing scene” today as a column of 8,000 to 10,000 people flooded past his embassy following a group of about 800 monks.

They were trailed by four truckloads of military men, watching but not taking action. The diplomat, in keeping with embassy policy, spoke on condition of anonymity.

According to news reports and telephone interviews from Myanmar, which is sealed off to foreign reporters, the day began with a confrontation at the giant, gold-spired Shwedagon Pagoda, which has been one focus of the demonstrations.

In the first reported violence in nine days of demonstrations by monks in the country’s main city, Yangon, police with riot shields dispersed up to 100 monks who were trying to enter the temple, firing tear gas and warning shots and knocking some monks to the ground. As many as 200 monks were reported to have been arrested at the pagoda.

Several hundred monks then walked through the city to the downtown Sule Pagoda, another focus of the demonstrations, where truckloads of soldiers had been seen arriving Tuesday. Another violent confrontation was reported here, at which more shots were fired and a number of arrests were made.

Tens of thousands of people were reported to be demonstrating in the streets of Mandalay, the country’s second largest city.

The demonstrations have grown from several hundred people protesting a fuel price rise in mid-August to as many as 100,000 Sunday, led by tens of thousands of monks in the largest and most sustained antigovernment protests since 1988.

That earlier peaceful uprising was crushed by the military, which shot into crowds, killing an estimated 3,000 people. It was during the turmoil a decade ago that the current military junta took power in Myanmar, and it has maintained its grip by arresting dissidents, quashing political opposition and using force and intimidation to control the population.

Now, emboldened by the presence of the monks, huge crowds have joined the demonstrations in protests that reflect years of discontent over economic hardship and political repression.

At first, the government held back as the protests grew. It issued its first warning Monday night, when the religious affairs minister said the government was prepared to take action against the protesting monks.

On Tuesday night, the government announced a dawn-to-dusk curfew, banned gatherings of more than five people and placed the cities of Yangon and Mandalay under what amounts to martial law. Troops began taking up positions at strategic locations around Yangon and attempted to seal off five of the largest and most active monasteries.

As the protests grew, public figures began to come forward, and on Tuesday the government arrested the first of them, a popular comedian, Zarganar, who had urged people to join the demonstrations. He had irritated the government in the past with his veiled political gibes.

The crackdown today came in the face of warnings and pleas from around the world to refrain from the kind of violence that has made the country’s ruling generals international pariahs.

At the United Nations, President Bush on Tuesday announced a largely symbolic tightening of American sanctions against the government. Today, British prime minister, Gordon Brown, called for a United Nations Security Council meeting on the situation. The European Union threatened to tighten its own sanctions if violence was used.

Reuters reported Mr. Brown, who was speaking to reporters in Britain, as saying:: “I hope the Security Council will meet immediately, meet today, and discuss this issue and look at what can be done.” He said the first step should be to send a United Nations envoy to Burma. The Dalai Lama and Desmond Tutu, the former South African archbishop and anti-apartheid campaigner, have spoken out in support of their fellow Nobel Peace Prize laureate, Daw Aung San Suu Kyi, Myanmar’s pro-democracy leader, who has been held under house arrest for 12 of the last 18 years.

The junta was also hearing the message directly from Yangon-based diplomats. The British ambassador, Mark Canning, said he met with a government official Tuesday to urge restraint.

“You need to look very carefully at the underlying political and economic hardships,” he said he told the official. “The government must also understand what this is about — not fuel prices, but decades of dissatisfaction.”