The Myanmar junta poured troops and police armed with rifles into central Yangon on Tuesday in an attempt to end the biggest demonstrations against military rule in nearly 20 years.

Hundreds of them surrounded the Sule Pagoda, focus of two days of mass protests led by thousands of maroon-robed monks, and appeared to be preparing to seal off the area, witnesses said.

In another possible sign of a looming confrontation, a well-placed source said detained democracy icon Aung San Suu Kyi was moved to the notorious Insein prison on Sunday, a day after she appeared in front of her house to greet marching monks.

Some analysts said the junta was been caught off guard by the speed with which protests mushroomed from sporadic marches against fuel prices in mid-August to massed demonstrations against 45 years of military rule a month later.

On Tuesday evening, soldiers moved in on Sule Pagoda after the end of hours of peaceful protest by tens of thousands of people who turned up despite the junta’s threat to use force.

The area around the pagoda, which includes City Hall, was the scene of the worst bloodshed during a crackdown on nationwide pro-democracy protests in 1988 in which 3,000 people are thought to have been killed.

Tuesday echoed with reminders of one of the darkest days of Myanmar’s modern history, starting with vehicles bearing loudspeakers touring the city blaring out threats of action under a law allowing troops to break up illegal protests.

People arrived in huge numbers anyway and in Taunggok, a coastal city 250 miles (400) to the northwest, about 40,000 monks and civilians took to the streets, witnesses said.

They were led in Yangon by 10,000 monks chanting “democracy, democracy” and, in a gesture of defiance, some waved the bright red “fighting peacock” flag, emblem of the student unions that spearheaded the 1988 uprising.

The streets were lined with people clapping and cheering as the column of monks stretched several blocks on their march from the Shwedagon Pagoda, the Southeast Asian nation’s holiest shrine and symbolic heart of the campaign, to the Sule Pagoda.

The international community pleaded with the generals to avoid another bloodbath.

British Ambassador Mark Canning told Reuters two ministers had assured him the protests “would be dealt with in a ‘correct’ fashion, whatever that means”.

But the chilling message behind the loudspeaker warnings was lost on nobody in Yangon, a city of 5 million people, a week after monks started marching in protest against warning shots being fired over the heads of fellow monks.

“I’m really worried about the possible outbreak of violence,” a street vendor said. “We know from experience that these people never hesitate to do what they want.”

Ethnic Karen rebels on the Thai border told Reuters troops of the 22nd Division had been redeployed to Yangon.

That division played a major role in the 1988 carnage and the report lent weight to threats against senior monks issued by Religious Affairs Minister Brigadier-General Thura Myint Maung.

State radio quoted him as saying action would be taken against senior monks if they did not control their charges in protests he said were fomented by political extremists.

China, the closest the junta has to a friend, has been making an effort recently to let the generals know how worried the international community is, a Beijing-based diplomat said.

On Tuesday, China said it “certainly hopes Myanmar can maintain stability and resolve the issue in its own way”, but left it unclear clear what kind of diplomatic pressure it was exerting on the generals behind the scenes.

Other countries urged the generals to address the grievances of Myanmar’s 56 million people who, in the past 50 years, have watched their country go from being one of Asia’s brightest prospects to one of its most desperate.

U.S. President George W. Bush said in a speech at the United Nations he would tighten economic sanctions “on the leaders of the regime and their financial backers” and expand a visa ban on “those responsible for the most egregious violations of human rights”.

However, the junta has lived with sanctions for years.

U.N. special envoy Ibrahim Gambari said he was praying the generals opted for compromise.

“For the sake of the people of Myanmar, for the sake of neighboring countries and for the sake of Myanmar’s place in the world, we certainly hope that the same reaction that took place in 1988 will not be the case now,” he told CNN.