Protesters appeal for talks after four days of clashes in Bangkok

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

"The government must order a ceasefire and troop withdrawal first, then we will... call back our people who are outside," he said, referring to hundreds of Red Shirt militants who have been fighting Thai troops.

However, Nattawut said the United Nations must serve as a mediator in the talks because "we don't see any neutral and just organisations".

There was no immediate response to the offer, but it raised a glimmer of hope for ending the violence.

As he spoke protesters dragged away the bodies of three people – who they said were shot dead by army snipers – as soldiers blocked major roads and pinned notices of a "Live Firing Zone."

A towering column of black smoke rose over the city today as protesters facing off with troops set fire to barricades. Elsewhere, they doused a police traffic post with petrol and torched it as sporadic gunfire rang out.

The Red Shirts have occupied a one square mile zone, barricaded by tires and bamboo spikes, in one of the capital's wealthiest areas, Rajprasong, since mid-March to push their demands for Prime Minister Abhisit Vejjajiva to resign immediately, dissolve Parliament and call new elections.

The Red Shirts, drawn mostly from the rural and urban poor, say the coalition government came to power through manipulation of the courts and the backing of the powerful military, and that it symbolises a national elite indifferent to the poor.

However, Thailand's prime minister has defended the deadly army crackdown, saying the country's very future was at stake.

"I insist that what we are doing is necessary," Prime Minister Abhisit Vejjajiva said in a defiant broadcast on national television.

"The government must move forward. We cannot retreat because we are doing things that will benefit the entire country."

But one protest leader warned: "The situation right now is getting closer to a civil war each minute.

"Please don't ask us how we are going to end this situation, because we are the ones being killed."

At least 24 people have been killed and more than 194 wounded since Thursday.

Previous violence since the protest began in mid-March caused 29 deaths and injured 1,640.