Tue Sep 25, 11:34 PM ET

YANGON - Troops and riot police took up positions outside at least six big activist monasteries in Yangon on Wednesday as Myanmar's junta tried to prevent monks leading new protest marches against military rule, witnesses said.

Hundreds more waited in a park behind the Sule Pagoda, the city centre focus of the biggest protests against the generals in 20 years, apparently prepared to prevent any repetition, they said.

There was no immediate word from the monks on whether they would risk their first major confrontation with the junta by trying to march again despite fears of a repetition of the bloody end to a 1988 uprising, primarily in the Sule Pagoda area.

If they did, they would face hundreds of security personnel who poured into the area after a huge demonstration ended on Tuesday.

Their arrival was the first significant action by the junta against protests which grew from handfuls of people marching against sudden huge fuel price rises last month into mass demonstrations against military rule.

Maroon-robed monks, revered in the staunchly Buddhist nation, have led the way, drawing in people first to watch, then to applaud, then to march with them. On Tuesday, they clogged several blocks of a city centre road.

The junta, which so far appears to be reluctant to risk a repetition of 1988, when an estimated 3,000 people were killed, waited until demonstrators had left on Tuesday to move soldiers and riot police into the area.

It also waited late into the evening, when most people in Yangon, a city of 5 million, and the second city of Mandalay, home to about 800,000, had gone home to send loudspeaker trucks into the streets to announce a dusk-to-dawn curfew.

It appeared the generals did not use radio and television because they have only national networks and on Wednesday morning few outside the two main cities were aware curfews had been imposed.

ACTIVISTS ARRESTED

But they picked up at least two activists overnight, relatives said.

Prominent comedian Za Ga Na, who had joined the monks on Monday in urging people to support the protests, was arrested at his home in Yangon along with activist Win Naing, relatives said.

In another move against monks, whose leadership on Monday was told to rein them in or face military force, a bus owner said drivers had been ordered not to pick up monks.

The escalating tension in the Southeast Asian country formerly known as Burma gripped the annual U.N. General Assembly in New York, where world leaders -- mindful of the 1988 violence -- called on the junta to exercise restraint.

U.S. President George W. Bush, in a speech to the assembly, called on all countries to "help the Burmese people reclaim their freedom" and announced fresh sanctions against the generals, their supporters and families.

The 27-nation European Union said it would "reinforce and strengthen" sanctions against Myanmar's rulers if the demonstrations were put down by force.

The U.N. human rights investigator for Myanmar, Paulo Sergio Pinheiro, said he feared "very severe repression."

"It is an emergency," he said, singling out China as a regional power that could play a "positive role" in defusing it.