Protesters Pull Back in Thailand : Unrest: Crowd leaves when troops fire into air on third day of violence. U.S. criticizes the government’s use of force.

Groups of pro-democracy demonstrators pulled back from a confrontation with security forces late Tuesday, dispersing when troops fired in the air after two nights of running gun battles turned Bangkok’s narrow streets into a war zone.

In the third day of Bangkok violence, nations around the world sent warnings to Thailand’s military government protesting the attacks on demonstrators. The United States assailed the Thai army’s use of deadly force and suspended a joint U.S.-Thai military exercise already under way.

Defiant Prime Minister Suchinda Kraprayoon, whom the pro-democracy forces are trying to oust, told a television audience that the violence had been inspired by Communist agents.

At least 21 people have been killed in the demonstrations, and hundreds have been wounded. Some estimates from opposition sources contend that the dead number in the hundreds and that soldiers have been trucking bodies away from the scene of clashes in an attempt to keep the official death count low.

As night fell in the capital, an eerie quiet settled on most of the city of 10 million, with shops and restaurants shuttered against a possible renewal of the violence. There was no traffic, and sidewalk vendors packed their carts and scurried home at 1 p.m.

Under a state of emergency, the government has banned gatherings of more than 10 people. The sale of gasoline was banned, and city buses were kept off the streets to prevent their falling into the hands of the protesters.

About 2,000 protesters gathered at a bridge across the Chao Phrya River, not far from where army troops stormed a downtown hotel early Tuesday, killing a number of demonstrators and wounding scores of others.

But after the night of bloodshed, the demonstrators seemed subdued, with no speeches or shouted slogans. Navy and marine units guarded a bridge leading to the area of Tuesday morning’s killings.

The demonstrators were given 30 minutes to disperse and left the area after a few cursory shots were fired in the air.

Not far away, about 3,000 demonstrators were gathered at a local police station, reportedly threatening to burn down the building unless detained protesters were immediately released. Reports in the Bangkok press estimated that up to 2,000 people were being held.

There was no word on the condition of Chamlong Srimaung, the pro-democracy leader whose arrest Monday triggered the nation’s worst political violence since 1976.

Early Tuesday, angry demonstrators torched the government tax office and public relations bureau, both four-story buildings. They also burned trucks, buses, oil tanker trucks and cars.

The demonstrations are aimed at forcing the resignation of Suchinda, a former commander in chief of the Thai armed forces who was appointed to the prime minister’s job April 7 by five pro-military parties. The protesters, many of them from Thailand’s growing class of educated office workers, want an elected prime minister.

In his television address, Suchinda said, “The leaders of last night’s demonstration which caused the violence were from the Communist Party and this former military man”--an apparent reference to retired Gen. Chaovalit Yongchaiyudh, an opposition party leader.

Communism was one of the political bogymen of the 1960s in Thailand, but it is rarely mentioned in current political debate.

Meanwhile, there were wire service reports Tuesday that the Bangkok unrest had spread. Tens of thousands reportedly gathered at a public park in Pattalung in the south and 10,000 in Khonkaen in the north. Another 10,000 people stood still in memory of the dead in the resort city of Phuket.

In Washington, the State Department advised U.S. citizens to defer travel to Bangkok. Spokeswoman Margaret Tutwiler said the U.S. government “cannot accept the use of deadly force” by Thai troops against protesters. She said the United States has suspended the Cobra Gold military exercises, which began three weeks ago and were to involve about 10,000 American troops in joint maneuvers with the Thai army through the end of this month.

The Bush Administration suspended about $60 million in economic and military aid to Thailand last year after a military coup.

Times staff writer Norman Kempster in Washington contributed to this article.