'Live firing zone'
His tough talk came hours after the Thai military declared "live firing zone" in Bangkok in its attempt to clear red shirt protesters from their encampment site in the capital.
But the protesters, seeking the prime minister's resignation and early elections, seemed to be in no mood to capitulate.
They responded with sporadic attacks on the army's positions, using petrol bombs to torch vehicles, and attempting to barricade their camp with piles of burning tyres.
As soldiers encircled the protest site, gunfire and explosions were heard in the streets surrounding the protesters' camp.
Al Jazeera's Tony Birtley, reporting from Bangkok, said that there was a lot of tension near the city's commercial centre.
"Every street corner is manned by police or soldiers, but there are protesters walking around with wooden clubs and other weapons."
He said that many of the streets were blocked off by barbed-wire, but people were still moving around.
Pictures circulated on Saturday showed army snipers taking positions in buildings in the Rajprasong business district.
Witnesses reported that about 2,000 protesters had massed on a main road leading to Bangkok's commercial centre on Saturday, about 2km from an area held by troops.
Al Jazeera's Aela Callan, also reporting from Bangkok, said television footage appeared to show troops were firing indiscriminately, with reporters covering the protests being shot at in some incidents.
"It's a very confusing situation," she said. "What we're going to have to watch for now is the reaction of the red shirts."
|Protesters have fought back with burning tyres and petrol bombs [AFP]
She said some red shirt sources in the northeast of Thailand had told her they were being prevented from sending bus loads of supporters to join the protests in Bangkok, while other more "hardline" red shirts were looking at more creative ways to bring reinforcements into the city.
"There are still thousands of people down there and there are still thousands that are willing to defend the barricades," she said.
Sean Boonpracong, a red shirt spokesman, called on the army to end its operations against the protest camp saying the two sides were unmatched.
"We want the army to cease fire," he told Al Jazeera.
"We really seriously want peace. We are really concerned at what is taking place."
Troops had begun encircling the protest site since Thursday evening after a deadline set by the military for the protesters to disperse expired. Clashes broke out almost immediately and 16 people were killed on Friday.
The face-off capped weeks of political turmoil in Thailand with the red shirts - predominantly supporters of ousted prime minister Thaksin Shinawatra - converging on the capital to press for the current government's resignation.
Abhisit had offered to call new elections if red shirts ended their two-month protest, but the demonstrators have insisted that the country's deputy prime minister must first be charged for the deaths of 25 red shirt supporters.
Panitan Wattanayagorn, a spokesman for the Thai government, told Al Jazeera on Saturday that discussions on holding new elections could only begin once the protesters disperse.
"When the protest ends, [the prime minister] will resume implementing the reconciliation plan and also consider the election after that. The election date was set on the 14 of November, but was rejected by the red shirt people," he said.