RANGOON, Burma — A U.N. envoy failed to meet with Burma’s top two junta leaders in his effort to persuade them to ease a violent crackdown on anti-government protesters, but he was allowed a highly orchestrated session yesterday with a detained opposition leader, Aung San Suu Kyi.

The military government, meanwhile, flooded the main city of Rangoon with troops, swelling their numbers to about 20,000 by yesterday and ensuring that almost all demonstrators would remain off the streets, a diplomat said. Scores of people also were arrested overnight, further weakening the flagging uprising against 45 years of military dictatorship. The protests began August 19 when the government sharply raised fuel prices, then mushroomed into the junta’s largest challenge in decades when Burma’s revered monks took a leading role.

One protest was reported yesterday in the western state of Arakan, were more than 800 people marched in the town of Taunggok, shouting “Release all political prisoners!” Police, soldiers, and junta supporters blocked the road, forcing them to disperse, a local resident said.

Ibrahim Gambari, the U.N.’s special envoy to Burma, was sent to try to persuade the notoriously unyielding military junta to halt its crackdown. Soldiers have shot and killed protesters, ransacked Buddhist monasteries, beaten monks and dissidents, and arrested an estimated 1,000 people in the last week alone.