BANGKOK - Thailand's premier said Thursday he has ordered a probe into reports that two men whose bodies were found gagged and bound in a river were anti-government protesters who rallied here this week.

Violent street protests raged in Bangkok Monday, leaving two dead and 123 injured, but so far there have been no confirmed fatalities among the "Red Shirt" demonstrators loyal to ousted premier Thaksin Shinawatra.

Prime Minister Abhisit Vejjajiva has been intent on avoiding bloodshed, which would be highly damaging politically. The two people whose deaths were reported earlier were local residents who clashed with the protesters.

The Bangkok Post quoted a colleague of the dead men found Wednesday morning, who were both security guards, as saying they had set off on a motorbike Monday to join the mass rally outside Abhisit's offices at Government House.

Their bodies were found floating in Bangkok's main river, with their hands tied behind their back. They had been badly beaten and had head injuries.

Abhisit said he had ordered a special investigation, but that the pair were still alive when the troubles ceased in the early hours of Tuesday.

"I have investigated and learned that these two were still alive on the night of April 13 and until the early morning of the 14th," he told a press conference.

"If you can recall, there was no further campaign (by security forces) on the morning of April 14," he said.

Police said there was no confirmation the pair were at the protest rally and that robbery was a more likely motive because their motorcycle was missing.

"The official investigation has not yet found their deaths are related to the political rally," police investigator Lieutenant Colonel Virat Petcharat told AFP.

The rally outside Government House broke up Tuesday after troops threatened to use force against thousands of demonstrators who had massed there for three weeks.

The night before, as soldiers tightened their grip on the protesters, local residents clashed with the Red Shirts, and two residents aged 19 and 54 were shot and killed.