
Maj Gen Kattiya Sawasdipol, an army officer, said thousands of pro-government protesters were setting up tents near the army headquarter.
The area was only a few hundreds away from the Government House and was ironically very close to the first rally site of People's Alliance for Democracy when it attempted to oust former premier Thaksin Shinawatra more than two years ago.
"I do not know what would happen next because the rival protersters are very close to each other, Kattiya said.
Anti-riot police and soldiers who were sandwiched near the Government House at 3 am on Tuesday could control the situation after pro-and anti-government protesters clashed in the first outbreak of violence that killed at least one man and injured dozens.
Hundreds of soliders have moved into the clash area to help the police order amid extremely high tension.
TV reports said a man, Narongchai Kobthaisong, died of wounds after being hit by hard objects. It was not known for certain whether he was one of the protesters or which side he was on.
He was the first Thai to have died from violence stemming from the on-going political crisis. Details remained sketchy. The clashes between anti-government protesters belonging to the People's Alliance for Democracy and pro-government demonstrators took place in "several spots" around Government House which has been occupied by the PAD since last week.
Hundreds of anti-riot soldiers and police were deployed to the site to prevent more violence and confrontation. They were caught in between the rival protesters near the Makkawan Bridge. The protesters were shouting at each other but a semblance of order was restored before 4 am.
Latest hospital reports confirmed 38 people were injured, three of them by gunshots.
They were being treated at the Vajira Hospital, Ratchavithi Hospital, Central Hospital, Ramathibodi Hospital, Hua Chiew Hospital, and Mission Hospital.
A reporter told Thai PBS said he believed molotov cocktails may have been thrown.
A PAD leader Suriyasai Katasila said some of the pro-government protesters were armed with guns and they fired at PAD demonstrators.
"It was like the situations leading up to October 6," he said, referring to the infamous Thammasat massacre in 1976. An emotionally-choked Suriyasai said incidents leading to the clash were something Prime Minister Samak Sundaravej "must have been aware of".
"One PAD member was shot at," Suriyasai said. "I don't know if he's dead or not."
Army Commander in Cheif Gen Anupong Paojinda said the army will help police to handle the situaiton and prevent it from escalating.
"This should not have happened," he said.
He said he ordered deployment of hundreds of anti-riot soldiers armed with shields and batons to stop the clash and to prevent it from escalating.
However he said what the army could do for now is only to help police stop the clash.
At 1.20am, hundreds of pro-government protesters, armed with batons, axes and big knives, marched from Sanam Luang to the Government House. The pro-government rally at Sanam Luang began on Saturday, amid fears of violence.
After midnight (early Tuesday morning), the pro-government protesters managed to break through the police lines who guarded the area. Their proclaimed intention was to "seize back" Government House from the PAD.
As of 1.40am, when they arrived at Makkawan Bridge, they clashed with guards of People's Alliance for Democracy who were deployed to guard the area. The area is only a few hundred metres from Government House.
Shinawatra Pabunchart, leader of pro-government protesters claimed that his men have already surrounded the Government House at 2am on Tuesday in a bid to oust anti-government protesters from the Government House.
He said he will allow the protesters in the Government House to go out but wil not allow anybody to enter the compound.
He said his group has no choice but to do so because many people were disagreed with the PAD-led protests and its seizure of the Government House.
He claimed that more people from other provinces will travel to Bangkok to join the confrontation with the PAD protests.
He said his group had no choice but to move his people to the Government House as the government could not handle the situation.
PAD leader Suriyasai Katasila said the pro-government protesters attacked PAD's guards around the site.
He claimed that one of his men was shot and was rushed to a hosptial nearby.
A reporter confirmed that she heard several gunshots. She also saw the injured man who she said seemed to have gunshot wounds and his body was soaked with blood.
Suriyasai said that it is estimated that dozens of protesters of both sides were injured.
He alleged that police deploying near the site allowed the pro-government protesters to march to be near the Government House. Suriyasai bitterly accused Prime Minister Samak of turning a blind eye to obvious signs that violence was going to happen.
"I don't want to say he had a hand in this, but you know him and October 6," the PAD leader said.
Some of pro-government protesters were seen marching while some others rode on motorcycles.