Thailand will impose a curfew Sunday and send Red Cross workers to evacuate women and children from Bangkok's deadly protest zone where 25 people have been killed in four days of street battles between anti-government demonstrators and troops.
A towering column of black smoke rose over the city Sunday as protesters facing off with troops set fire to tires serving as a barricade. Elsewhere, they doused a police traffic post with gasoline and torched it as sporadic gunfire rang out.
The government said a curfew has become necessary to stop the armed members of the so-called Red Shirt protest movement. Journalists have seen some of them carrying guns, but most have used homemade fire bombs and fireworks.
''We cannot let people with weapons in their hands walk around here and there,'' army spokesman Col. Sansern Kaewkamnerd said.
''Terrorist groups have tried to create a situation where shots are fired at military and police officers to instigate misunderstanding among them that officers are attacking each other,'' he said.
The timing and the exact locations of the curfew will be announced later, he said.
The spiraling violence has raised concerns of sustained, widespread chaos in Thailand -- a key U.S. ally and Southeast Asia's most popular tourist destination that promotes its easygoing culture as the ''Land of Smiles.''
Speaking on his weekly television program, Prime Minister Abhisit Vejjajiva insisted he was left with no choice but a military operation to end the country's two-month-old crisis.
''Overall, I insist the best way to prevent losses is to stop the protest. The protest creates conditions for violence to occur. We do realize at the moment that the role of armed groups is increasing each day,'' he said.
The Red Shirts have occupied a 1-square-mile (3-square-kilometer) zone, barricaded by tires and bamboo spikes, in one of the capital's ritziest areas, Rajprasong, since mid-March to push their demands for Abhisit to resign immediately, dissolve Parliament and call new elections.
The Red Shirts, drawn mostly from the rural and urban poor, say Abhisit's coalition government came to power through manipulation of the courts and the backing of the powerful military, and that it symbolizes a national elite indifferent to the poor.
Sansern said the government will send the Red Cross and voluntary organizations into the protest zone to ''invite or persuade people, especially women, children and older people to leave the area.''
About 5,000 people are believed camped in the zone, down from about 10,000 before fighting started Thursday after a sniper shot and seriously wounded a Red Shirt leader, a former army general who was the Red Shirt military strategist. His condition worsened Sunday, doctors said.
After his shooting, fighting quickly spread to nearby areas, which became a no-man's land as the army set up barriers in a wider perimeter around Rajprasong. The area already resembles a curfew zone with no public transport or private vehicles. Most shops, hotels and businesses in the area are shut. The government has shut off power, water and food supplies to the core protest zone. Schools were ordered shut Monday in all of Bangkok.
At least 54 people have been killed and more than 1,600 wounded since the protests began mid-March, according to the government. The dead include 25 killed since Thursday.
''I'm asking Abhisit not to shoot children, women and old people. Come kill us (men) instead,'' said a Red Shirt leader, Jatuporn Prompan. ''Once the authorities stop shooting at protesters, the death toll will stop rising.''
On Saturday, soldiers blocked major roads and pinned up notices of a ''Live Firing Zone'' in one area of Bangkok. Demonstrators dragged away the bodies of three people from sidewalks in that area -- shot by army snipers, they claimed.
The New York-based Human Rights Watch on Saturday called on the Thai government to revoke the fire zones and negotiate an end to the fighting.
''It's a small step for soldiers to think `live fire zone' means `free fire zone,' especially as violence escalates,'' the rights watchdog said in a statement.
The clashes are the most prolonged and deadliest bout of political violence that Thailand has faced in decades despite having a history of coups -- 18 since it became a constitutional monarchy in 1932.
The crisis appeared to be near a resolution last week when Abhisit offered to hold elections in November, a year early. But the hopes were dashed after Red Shirt leaders made more demands.
The political uncertainty has spooked foreign investors and damaged the vital tourism industry, which accounts for 6 percent of the economy, Southeast Asia's second largest.
The Thai Red Cross said its blood supplies are running low and invited people to donate blood.
The Red Shirts especially despise the military, which forced Thaksin Shinawatra, the populist premier favored by the Red Shirts, from office in a 2006 coup. Two subsequent pro-Thaksin governments were disbanded by court rulings before Abhisit became prime minister.
Bangkok since March, calling on women and the elderly to leave the camp by Monday afternoon.
The Red Cross has been asked to help coax people out of the camp, where protesters are calling on PM Abhisit Vejjajiva to resign.
One protest leader said Thailand was close to "civil war" after clashes with soldiers killed at least 25 people.
Several hundred protesters are gathering in another part of the city.
Soldiers have taken up positions beside a road leading to the camp, where witnesses say they are firing live rounds, apparently targeting anyone who comes near them.
Mr Abhisit has postponed the new school term in the city for a week, but a planned curfew has been cancelled.
Thai television has shown footage of women and children leaving the protest site.
The fighting flared on Thursday as the army moved to isolate a fortified protest camp.
Thousands of people who say Mr Abhisit came to power undemocratically remain behind makeshift barricades of rubber tyres, sandbags and bamboo stakes in the Ratchaprasong commercial district.
The protesters are known as red-shirts, after the colour they have adopted.
They want the prime minister to step down to make way for new elections.
Red-shirt leaders have been calling for reinforcements, but protesters coming from elsewhere in the country have been unable to breach the military cordon, and are congregating nearby.
Several hundred red-shirt suppporters have gathered around a mobile stage set up in central Bangkok's Klong Toey area, and protest leaders have called for a rally at another mobile stage in the north of the city.
In a televised address on Saturday, Mr Abhisit said the army would not back down in its operation to clear the protesters.
"We cannot leave the country in a situation where people who don't obey the law are holding hostage the people of Bangkok, as well as the centre of the country," he said.
"We can't allow a situation where people set up armed groups and overthrow the government because they don't agree with it."
Mr Abhisit has said that a few armed "terrorists" are among the protesters.
An army spokesman said the military was planning to enter the protesters' camp if they did not disperse, but gave no timetable.
"There is a plan to crack down on Ratchaprasong if the protest does not end," said the spokesman, Col Sunsern Kaewkumnerd.
"But authorities will not set a deadline because without effective planning there will be more loss of life."
The BBC's Chris Hogg in Bangkok says the army's actions are like squeezing a balloon full of water - they are just pushing protesters into a different part of the city.
Black smoke drifted into the air over Bangkok on Sunday morning but the streets were mostly quiet after three days of fierce battles that saw soldiers fire live rounds and rubber bullets at protesters who threw stones, petrol bombs and shot fireworks in return.
The army has declared live fire zones in some areas as it attempted to cut off the camp from supplies and reinforcements.
Around 200 people have been injured since the latest violence broke out on Thursday, and 27 people have been sent to jail, each given six-month sentences. All the fatalities have been civilians.
More than 50 people have been killed and at least 1,500 wounded in total since the protests began in mid-March, Thai officials have said.
Despite claims by the Thai government that the situation was under control and its soldiers had only fired in self-defence, army snipers have been accused of targeting protesters. Footage from Bangkok on Saturday showed red-shirts dragging gunshot victims to safety.
The violence escalated on Thursday after a renegade general who supports the protests was shot in the head by an unknown gunman.
Gen Khattiya Sawasdipol, better known as Seh Daeng (Commander Red), is in a critical condition.
The latest clashes have raised questions about the stability of Thailand, South-East Asia's second-largest economy.
"The current situation is almost full civil war," said one of the protest leaders, Jatuporn Prompan. "I am not sure how this conflict will end."
Many of the protesters are from poor rural areas in northern Thailand where support is still strong for former Prime Minister Thaksin Shinawatra, who was ousted in a 2006 coup.
They say Mr Abhisit was put into power in a parliamentary vote by an alliance of the Bangkok elite and the military and want him to dissolve parliament and call fresh elections.
He had offered polls in November - but the two sides failed to agree a deal because of divisions over who should be held accountable for a deadly crackdown on protests last month.
Mr Thaksin has called on the government to withdraw troops and restart negotiations. He is living abroad to avoid a jail term on a corruption conviction.