Thai troops fired at protesters on Saturday on the third day of fighting that has killed 17 people on Bangkok's streets as soldiers struggle to isolate a sprawling encampment of demonstrators seeking to topple the government.
Soldiers, many crouched behind sandbags, fired live rounds at hundreds of protesters who fought back with petrol bombs, rocks and crude homemade rockets in clashes on Bangkok's usually congested Rama IV road near the business district.
A volunteer medical rescue worker was shot and feared dead on Rama IV, and at least four others were shot, including one in the head, and evacuated, witnesses said.
"The troops may be making some progress on sealing the area but at a great cost," said Thitinan Pongsudhirak, political scientist at Chulalongkorn University, adding rising casualties could weaken Prime Minister Abhisit Vejjajiva.
"Is the government successfully dispersing the crowd and progressing toward ending the crisis? The answer is no, not so far, and it's a long way to go," he added.
At Din Daeng intersection, north of the protest site, three bodies were evacuated on stretchers, a Reuters witness said, indicating the death toll could rise. Two suffered head wounds.
That followed a long night of grenade explosions and sporadic gunfire as the army battled to set up a perimeter around the 3.5 sq-km (1.2 sq-mile) barricaded encampment where thousands refuse to leave, including women and children.
"We'll keep on fighting," said Kwanchai Praipana, a leader of the red-shirted protesters, calling on Abhisit to resign to take responsibility for the deadliest political crisis in 18 years.
He said supplies of food, water and fuel were starting to run thin as their usual delivery trucks were blocked but that they had enough to last "days".
Hardcore protesters set fire to vehicles, including an army truck, and hurled rocks at troops who set up razor wire at checkpoints when asked to show identification to prevent people from joining the mostly rural and urban poor "red shirts".
A sign at one intersection warned residents not to enter a "live bullet area". Another warned of a "rubber bullet area."
The crisis has paralysed Bangkok, squeezed Southeast Asia's second-biggest economy, scared off tourists and choked investment in one of Asia's most promising emerging markets.
It has also stunned "Bangkokians" as one of the world's most bustling cities and tourist hot spots descends into a war zone.
"My ears are ringing with all the shooting last night," said Ratana Veerasawat, a 48-year-old owner of a hole-in-the-wall grocery store north of the protest encampment where many residents were leaving for safer locations.
"It's just awful and getting worse. Best to leave now."
"Unlikely to end quickly"
United Nations Secretary-General Ban Ki-Moon expressed concern over "the rapidly mounting tensions and violence".
"He strongly encourages them to urgently return to dialogue in order to de-escalate the situation and resolve matters peacefully," his spokesman said in a statement.
The Canadian government urged both sides to return to talks after a Bangkok-based Canadian journalist was shot three times, one of four journalists wounded in fighting that has spiralled into chaotic urban warfare where front lines shift quickly.
The government said on Friday it would restore order "in the next few days" as the city of 15 million people braced for a final crackdown in the area of high-end department stores, luxury hotels, embassies and expensive residential apartments.
Protest numbers in the main encampment dropped overnight but several thousand remained, many singing and listening to speeches. Some leaders, including the movement's chairman, haven't been seen for days. Several wore flak jackets, fearing snipers. They face criminal charges connected to the protests.
"I am not scared," said Sanae Promman, a 37-year-old protester frying vegetables in a wok under a tent at the site. "Some of my friends have left because they are scared but many are still here to fight. We will fight until we die if we must."
They're barricaded behind walls of kerosene-soaked tyres, sharpened bamboo staves, concrete blocks and razor wire.
"It's unlikely to end quickly," said a source close to army chief Anupong Paochinda, fearing more protesters would arrive to surround and attack soldiers.
The Health Ministry said at least 17 people had been killed and 161 wounded in the latest fighting.
Before fighting began on Thursday with the shooting of a renegade general allied with the protesters, the two-month crisis had already killed 29 people and wounded about 1,400 -- most of whom died during an April 10 gun battle in Bangkok's old quarter.
The fighting is the latest eruption in a polarising five-year crisis between a royalist urban elite establishment, who back the prime minister, and the rural and urban poor who accuse conservative elites and the military's top brass of colluding to bring down two elected governments.
Those governments were led or backed by exiled former premier Thaksin Shinawatra, a graft-convicted populist billionaire ousted in a 2006 coup who is a figurehead of the protest movement.
The red shirts and their supporters say the politically powerful military influenced a 2008 parliamentary vote, which took place after a pro-Thaksin party was dissolved, to ensure the British-born, Oxford-educated Abhisit rose to power.
"I don't think many see the end of this protest as the end of the crisis," said Danny Richards, Asia editor at the Economist Intelligence Unit. "When there's an election, either side will reject the legitimacy of the other. We'll be back to square one."