At least one protestor has been killed, and five others wounded after protests in the capital turned aggresive yesterday.
Gunshots rang out in street fights between government supporters and their foes.
It was not immediately known who fired the shots or what side the victims were on. National Police Deputy Spokesman Anucha Romyanant said the dead man was a 21-year-old male with two bullet wounds said wire agency AP.
Tensions reached a peak after red-shirt supporters of the United Front for Democracy against Dictatorship (UDD), supporters of the government led by Ms Yingluck Shinawatra, began to make their way into the capital in busloads.
The Bangkok Post reported that the red-shirt supporters, estimated at about 70,000, converged at the city's Rajamangala Stadium. In earlier incidents, anti-government protesters attacked a bus and a taxi carrying red-shirt supporters near the stadium as fears of a confrontation grew.
The bus tyres were slashed but the driver managed to escape. No passengers were injured.
Even as thousands of red-shirt supporters streamed into the stadium, anti-government students from the university confronted them, leading to violence.
A local TV station reported that one red-shirt supporter was attacked by the students when he revved his motorcycle in front of them. He escaped with minor injuries.
The students later surrounded a taxi carrying a man wearing a red shirt and smashed its windows with sticks. The driver escaped. Ms Yingluck has defended her government's response to events, saying police were ready to protect state property but with "leniency" towards protesters.
But some red-shirt supporters want the government to do more.
UDD chairman Tida Thawornseth said yesterday that if the government could not protect public buildings, it would be up to the red-shirt supporters to show what "people power" really was.
And in a sign of the worsening situation in the capital, a senior police official said the about 3,000 troops will be deployed to reinforce security, AFP reported.
"From tonight there will be soldiers out to take care of security," police spokesman Piya Utayo said.
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