He said that at least one person was confirmed killed and one other critically wounded.
Sean Boonpracong, a red shirt spokesman, told Al Jazeera that Khattiya Sawasdipol, a former military general who was said to be in charge of security at the protesters encampment, was in hospital after being shot.
"We believe that this is the beginning of the army plan to crack down on us. We have been prepared for this for a long time," Boonpracong said.
Another protester was shot in the head and is believed to have died.
Witnesses reported that at least two other people were injured when troops opened fire after protesters charged them
Sealing off site
Security forces had been preparing to seal off the protest site and surround it with armoured vehicles from 1100 GMT, and would allow people to leave but not enter.
A leader of the anti-government protesters urged supporters to surround the armoured vehicles when they converged outside their protest site, in order to prevent them from being used to disperse the crowds.
"We will send out groups to surround these vehicles to prevent them from advancing," Jatuporn Prompan, a protest leader, told supporters.
"We believe the army will try to crack down this evening or tomorrow morning."
Hay reported that the government said they wanted the 'innocent protesters' to leave the area, and stressed that this was not a crack down.
The government had threatened to cut off power and water supplies to the Rajprasong neighbourhood of Bangkok, where the demonstrators are massed, if the protesters did not disperse by midnight local time (1700 GMT) on Wednesday.
That deadline came and went, but supplies were still available and the protesters unmoved after the deadline had passed.
The plan to choke off essential services to the demonstrators was put on hold because of the repercussions it would have on other residents, which include foreign diplomats, Sansern Kaewkamnerd, the spokesman for an agency in charge of suppressing the protests, said late on Wednesday.
'Government looking weak'
Al Jazeera's Aela Callan, reporting from Bangkok, said that Sawasdipol, who is also known as Seh Daeng, was shot in the head and was seriously injured.
"He is currently in hospital and his condition appears to be stable."
Callan said that sporadic gunfire and explosions had broken out in the Selong district area, where there has been gunbattles between protester and troops in the past.
"Right now I have been down to look at the area and the perimeter site appears very calm. The government has cut the street lights as they threatened to do," she said.
|Abhisit had offered to hold elections in November after dissolving parliament [AFP]
"However there is no sign of the armoured personnel carriers or the thousands of troops that have been brought into the area. They appear to be nowhere in sight and are perhaps staying out of sight to not inflame things further.
"We’ve seen ultimatum after ultimatum, deadline after deadline from the government and yet they have been unwilling to move in on protesters," she said, adding that some think that this is because the government do not have support from the military.
Korbsak Sabhavsau, the prime minster's secretary-general, said on Thursday that the government would not carry out elections as part of a peace deal with the so-called red shirt protesters until the demonstrations ended.
"It's clear that the red shirts have only verbally accepted to join the reconciliation roadmap but have not agreed to end the protests," Korbsak told the AFP news agency.
"Therefore it's impossible to hold elections as proposed."
The red shirts have said that they are not leaving until Suthep Thaungsuban, the deputy prime minister, is charged for his alleged role in a deadly crackdown on protesters on April 10.
They have held protests since March 12 calling for the dissolution of parliament and fresh elections.
The demonstrations have often brought parts of central Bangkok, the capital, to a standstill for long-periods and have included clashes with police, leaving 29 people dead and 1,400 injured.
"[Abhisit Vejjajiva], the prime minister, has said that if today everyone, including the government, can work freely and travel freely without disruption then there can be elections, but the situation is making no progress," Korbsak said.
"As there is no election, there is no need for house dissolution."
A deal on an amnesty for both sides could be the main sticking point for a successful reconciliation deal. Arrest warrants have been issued for many of the red shirts' chief leaders.
The red shirts initially called for immediate elections but agreed to a reconciliation deal this month in which Abhisit offered to dissolve parliament in the second half of September and hold polls on November 14.
They have said that the government is backed by the military and came to power undemocratically, via a 2008 parliamentary vote following a court ruling that ousted Thaksin Shinawatra, the former prime minster who is linked closely to the protesters.
Nattakorn Devakula, a political analyst, told Al Jazeera: "The red shirts did not take the offer [for November elections] which puts them into a very cornered, perhaps desperate, situation.
"At this point the red shirts have to take some sort of an offer otherwise it is going to push the government to take a harsh hand."