BANGKOK - Thai investigators said Monday there were grounds to charge former premier Somchai Wongsawat and other top officials over a violent crackdown on anti-government protests late last year.

The National Counter Corruption Commission (NCCC) said Somchai and his then-deputy prime minister Chavalit Yongchaiyudh had violated the law when they ordered police to disperse angry mobs who besieged parliament on October 7.

Two people were killed and nearly 500 injured that day as police clashed with demonstrators and used tear gas on the crowd.

"The commission found enough grounds to inform the accused... of the charges related to the dispersal of the demonstration, which led to people's death and injury," the NCCC statement said.

Somchai and Chavalit will have to present themselves to the commission to give their side of the story, before investigators decide whether to forward the charges to Thai prosecutors.

The pair face a charge of wrongfully exercising their duty resulting in injury, which carries a jail sentence of up to 10 years.

The commission also recommended disciplinary action against the current national police chief and his deputy over the protests, while three other senior police officers could also face criminal and disciplinary charges.

"I will not quit even though I know I will face pressure," national police chief General Patcharawat Wongsuwan told reporters. "I have done nothing wrong. I did what I did because I had an order from the government."

Supporters of royalist protest group the People's Alliance for Democracy (PAD) surrounded parliament on October 7 and trapped lawmakers inside as they intensified a campaign launched in May to topple the government.

Somchai is the brother-in-law of Thaksin Shinawatra, the deeply-divisive prime minister who was overthrown in a military coup in September 2006 and who currently lives in exile.

The PAD draws support from the old Thai power cliques in the palace, army and bureaucracy, and objected to the return to power of Thaksin's allies in the first post-coup elections in December 2007.

Protests peaked with the PAD occupation of Bangkok's two airports in late November and early December, which ended when a court dissolved the ruling party and removed Somchai from office over old vote fraud charges.