An escalating confrontation between Thai security forces and protesters who have occupied the heart of the capital appeared headed for further violence Sunday, after the government rejected a plea for UN-mediated peace talks.

Four days of street fighting between Red Shirt protesters and Thai soldiers in downtown Bangkok have left 30 people dead and another 232 wounded, according to Thailand's main emergency medical centre. Erawan Emergency Center said Sunday that all those killed were civilians.

The latest deaths raise to 59 the number of people killed in related violence since April 10.

Leaders of the protest movement, which is demanding the government step down and call new elections, offered Sunday to hold UN-mediated peace talks with the government, provided the army ended its crackdown immediately.

But Thai government spokesman Panitan Wattanayagorn quickly rejected the call. He said there was no reason for the army to withdraw since "authorities are not using weapons to crack down on civilians."

Panitan said Thailand is a sovereign nation and there was no need for the U.N. to get involved in internal matters and called on all groups using weapons to threaten security forces to "stop their actions immediately."

The government maintains it is only targeting armed "terrorists" among the Red Shirts, who have occupied a three-square-kilometre zone in the heart of downtown Bangkok for nearly two months.

A state of emergency, already in effect in 17 provinces, was extended Sunday to five more provinces. The emergency bans a gathering of more than five people and gives the military broad powers.

Schools were ordered shut on Monday in all of Bangkok and long lines formed at supermarkets outside the protest zone as people rushed to stock up on food.

Elliot Tepper, a professor of Asian studies at Carleton University, told CTV News Channel that the current crisis will likely deepen before it cools.

"The whole political fabric of Thaland is being tested," he said.

"This has been building for some time … (and) we're coming to the crunch. Compromise hasn't worked; the King's mild intervention didn't even work; what looked like a deal reached just a week ago fell apart, so military intervention seems to be at the moment the only way out."

A towering column of black smoke rose over the heart of Bangkok Sunday as protesters set fire to tires serving as a street barricade and doused police vehicles and traffic posts with gasoline and set them ablaze as sporadic gunfire rang out.

"We are willing to negotiate immediately. What's urgent is to stop the deaths of people. Political goals, political demands, or our fight can wait," Nattawut Saikua, one of the leaders, told reporters and supporters.

"The government must order a cease-fire and troop withdrawal first, then we will ... call back our people who are outside," he said, referring to hundreds of Red Shirt militants battling Thai troops in the streets of central Bangkok.

The fighting that began on Thursday has turned parts of a city known for its nightlife into a war zone.

Soldiers have encircled the protest zone in a wide perimeter and most of the fighting is taking place in the no-man's land in between. The Red Shirts have used homemade gasoline bombs, firecrackers, rocks and in some cases guns to attack troops positioned behind sandbag bunkers.

The soldiers have responded with rubber bullets and live ammunition and journalists have seen army snipers take aim through telescopic sights and fire to keep the attackers at bay.

With the Red Shirts' encampment in one of the capital's ritziest areas, Rajprasong, virtually besieged by the army, the protesters are running out of food and water and other supplies.

On Sunday, their leaders told the women and children among the protesters to move to a Buddhist temple compound within the protest zone. In Thai tradition, temples are considered safe havens and will not be entered by anyone bearing arms.

Somchai and Jintana Sawaaitrakul, holding the hands of their two daughters aged 8 and 6, carried their bags into the Pathumvanaram Temple.

"There were bombs and shooting here and there. We'd rather not stay in the area. One time there was an explosion. I hurriedly took the kids away," said Somchai.

A steady stream of families moved into the temple, carrying children and their stuffed toys including teddy bears. Some laid out straw mats on the floor and made themselves comfortable.

The government said it will send Red Cross and other voluntary groups into the protest zone to evacuate women, children, the elderly and the sick.

About 5,000 Red Shirts and supporters are believed camped in the protest zone, down from about 10,000 before fighting started Thursday.

Tepper said the protesters' demand that Prime Minister Abhisit Vejjajiva resign immediately, dissolve Parliament and call new elections could leave the country on the verge of civil war.

"It's not impossible unfortunately, although civil war may not be quite the term for it – prolonged civil unrest perhaps," the professor told CTV News.

"A lot of grenades have been tossed and right now the prognosis appears to be violence as the way out."

With files from The Associated Press