Jatuporn Phromphan, a protest leader, admitted that some demonstrators had gone home to celebrate the Thai New Year holidays, which began on Monday, but vowed to make a final stand at Government House.
"We will stay put. We will not back down," he said.
Preparing for battle
Some protesters were preparing themselves for more confrontations with the military on Tuesday after troops moved in on them early on Monday after weeks of relatively peaceful demonstrations.
Protesters felled trees and lay them across a main road between the troops and the centre of the protest, stockpiled rocks and bricks and doused with petrol buses they had commandeered and used to block streets.
Refusing the protesters' demand to resign and dissolve parliament, Abhisit Vejjajiva, the prime minister, urged the protesters to go home.
Abhisit praised the efforts of security forces, saying they used "soft means" and "prevented as much damage as possible", a view disputed by Thaksin Shinawatra, the exiled former prime minister ousted in a 2006 coup whom most of the protesters support.
In an interview with Al Jazeera, Thaksin accused the military of firing at protesters and covering up killings by taking dead bodies away.
Abhisit said the news that two people had been killed and 12 wounded in a gun battle between protesters and residents at Nang Lerng market was "a regrettable incident".
But he said "with the co-operation of the public, I believe success is near".
Reported clashes between Bangkok residents and protesters on Monday were probably a sign of frustration by the city's residents who are largely anti-Thaksin and firmly behind Abhisit's government, our correspondent explained.
They formed the core of the Yellow Shirts' protests last year against successive pro-Thaksin prime ministers that culminated in the shutdown of the city's two airports and court rulings ordering the dissolution of the government, paving the way for Abhisit to take power in December.
Bands of Yellow Shirts - a loose alliance of royalists, military and urban elites who oppose Thaksin - reportedly clashed with the Red Shirts on Monday night as well, our correspondent said.
Satit Wongnongtaey, a minister in the prime minister's office, said two men were shot dead in clashes between demonstrators and local residents on Monday.
More than 100 people were also injured in violence on Monday that raged for more than 12 hours as protesters fought a series of running street battles with armed soldiers.
Following calls by protest leaders for the Red Shirts to regroup at their Government House base from several flashpoints across the city, soldiers have ringed the area in what could be a final push to end the demonstrations that have rocked a country still reeling from last year's chaos and the global financial crisis.