Meanwhile, anti-government protesters in Bangkok have rejected talk of negotiations as they continue their occupation of key areas in the Thai capital -- the main shopping area and the city's historic district.
Medical officials in Thailand say more than a dozen people have been killed and more than 800 others injured in clashes between anti-government protesters and soldiers in the center of the capital, Bangkok. The demonstrators are demanding the resignation of Prime Minister Abhisit Vejjajiva. Mr. Abhisit has called for a full investigation into the violence and has refused to step down.
Speaking in a nationally televised address, Thai Prime Minister Abhisit Vejjajiva expressed condolences to the families who lost loved ones in Saturday's protest violence.
Mr. Abhisit said he regretted the bloodshed and loss life caused by the crackdown against anti-government protesters. He said there would be full investigations into the violence. He added he would not step down from power.
Thai Government spokesman Panitan Wattanayagorn said investigations would be wide ranging and that protest representatives would be invited to participate.
"We are committed to make sure that justice is served or being done," Panitan said. "We are ready to enter into the justice process to be examined. We are in the beginning asking independent academic institutions and the police autopsy unit to investigate the deaths of all people. We are also happy to invite representatives of the demonstrators to join the committee to examine the cause of the deaths of the people last night."
Panitan said four officers were killed and over 200 injured, with 90 in serious or critical condition. He accused some among the protesters of using weapons and tear gas and denied that soldiers used live rounds against the demonstrators.
Month-long protests turned violent after security forces attempted to move thousands of so-called "Red Shirt" protesters who are blocking key areas in the capital.
One protester, who identified himself as Mr. Gunn, witnessed the violence.
Mr. Gunn said helicopters had dropped tear gas and this was followed by troops moving into the area.
Security forces failed to disperse protesters from public places despite firing rubber bullets, tear gas and live ammunition. Protesters fought back with stones, guns and gasoline bombs.
Thai medical officials say a Japanese cameraman with the Reuters news agency and at least five soldiers are among those killed. More than 520 others were injured in clashes Saturday in other parts of Thailand's capital.
Late Saturday night protesters at the Phan Fah Bridge protest site brought the bodies of two UDD rally guards onto the stage, as the names of the dead were read out to the crowd.
Calm returned to the capital early Sunday, but anti-government protesters continue to occupy key intersections in the city. A state of emergency, declared by the government, remains in place.
The United States has called on both sides to show restraint and work out disagreements peacefully through earnest negotiation.