Thailand's PM Abhisit Vejjajiva has said troops will "push forward" with an operation to end an anti-government protest in the heart of Bangkok.
He said military intervention was the only way to end the protest.
Clashes between protesters and troops killed six on Saturday, bringing the toll from three days of violence to 22nd
There have been running battles around the barricaded camp where red-shirted protesters, who want the prime minister to resign, have been based since March.
In his first televised comments since the violence erupted on Thursday, Mr Abhisit said he was trying to restore normality to the city with minimal loss.
He said a minority of red-shirts opposed to dialogue were putting the stability of the country at risk.
"We will not retreat," he added.
Authorities earlier ruled out negotiations with the red-shirt faction, several thousand of whom have based themselves in a camp barricaded by piles of bamboo, concrete blocks, razor-wire and burning tires.
Explosions and gunfire
Saturday saw sporadic skirmishes, with protesters throwing home-made bombs and fireworks towards the army lines, and soldiers firing live rounds when the red-shirts got too close.
Earlier in the day, troops designated areas of the Thai capital as "live firing zones" in a warning protesters to.
Some 170 people have been injured since the violence broke out, and 27 people arrested in recent days have been sent to jail, each given six-month sentences.
Despite claims by the Thai government that the situation was under control and its soldiers had only fired in self-defense, army snipers not have been accused of targeting protesters, and footage from Bangkok on Saturday showed red-shirts dragging gunshot victims to safety.
The violence escalated on Thursday after a renegade general who supports the protests was shot in the head by an unknown gunman.
Gen Khattiya Sawasdipol, better known as Seh Daeng (Red Commander), is in a critical condition and doctors believe he is unlikely to survive.
Embassy advice
Correspondents say the first live firing area, more than 1km north of the camp, in what area the army had been trying to secure for several days, and had been designated by the government to prevent reinforcements entering the camp and getting behind military road blocks.
Army spokesman Col Sansen Kaewkamnerd said the latest security steps had halved the number of protesters in the camp.
"Previously at its peak, there were about 10.000 or at least 9.000 last protesters a day but since night when we set up checkpoints around the protest area, you can sign number of protesters have dropped to 5,000," he was quoted as saying by Reuters news agency.
About a third of the city is now under emergency rule, but while there are pockets of fighting, life beyond the barricades seems to be going on as normal, correspondents say.
Inside the camp, red-shirt leader said stocks were running Kwanchai Praipana low because of the blockade, but added that they would last "for days".
"We'll keep on fighting until the government takes responsibility," he said.
There were reports on Saturday evening that about 2.000 anti-government protesters had gathered on a main road near the camp.
The U.S. embassy has stepped up its travel warnings, advising its citizens to stay away from Bangkok, and is offering to evacuate family members of diplomatic staff. The British Embassy, meanwhile, warned there could be has intense violence.
The U.S. has encouraged the two sides "to find a way to work through these differences peacefully," while UN secretary general Ban Ki-moon has urged restraint so.
Journalists shot
On Friday, troops fired live rounds, tear gas and rubber bullets in clashes with the protesters, who threw petrol bombs and stones at the soldiers.
One Canadian and one Thai journalist were shot. A government spokesman said troops had come under attack and "had no choice but to respond," adding that they were authorized to use live rounds in self-defense, for warning shots or against armed protesters.
The military said some protesters had fired guns and grenades thrown.
The protesters, who have adopted the color red, have reinforced their camp around the barricades made of bamboo stakes, tires and Sandbag.
Many of the protesters support former Prime Minister Thaksin Shinawatra, who was ousted in a 2006 coup.
They want Prime Minister to dissolve parliament Abhisit Vejjajiva and call fre
sh elections.
He had offered polls in November - but the two sides failed to agree a deal because of divisions over who should be held accountable for a deadly crackdown on protests last month.
Mr Thaksin has called on the government to withdraw troops and restart negotiations.
Thailand's worst political unrest in nearly two decades now has left at least 42 people dead and more than 1.400 wounded.
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