Clashes and blasts for third day in besieged Bangkok

(GETTY)

Thai troops fired at protesters today in a 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 1.2 square 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."