BANGKOK, Thailand -- A former prime minister of Thailand was charged with murder Thursday in the latest twist in a political war between supporters and opponents of another ex-leader, Thaksin Shinawatra.

The murder charge against Abhisit Vejjajiva stems from the violent suppression of anti-government protests in 2010 when demonstrators were seeking to have Abhisit, Thaksin's rival, call early elections, saying he was installed in office illegitimately.

Thaksin was ousted as prime minister by a military coup in 2006 after being accused of corruption and disrespect to the monarchy.

The protests and crackdown left more than 90 people dead and about 1,800 injured in Thailand's worst political violence in decades.

Abhisit is accused by the Department of Special Investigation of allowing the unrestrained use of deadly force to quell the protest.

Speaking to reporters after meeting for more than four hours with DSI officials, Abhisit said he had formally acknowledged the charge against him, but denied he was guilty. He said he would present documents supporting his position after studying the charge more closely.

A court must still accept the case before it goes forward to trial.

DSI specifically found reason to believe Abhisit culpable in the death of a taxi driver because he allowed troops to use war weapons and live ammunition against protesters. A recent criminal court inquest had found security forces responsible for the man's death.

The shooting occurred during two months of demonstrations by Thaksin's supporters, known as the Red Shirts, who occupied a central intersection in the capital Bangkok. As tensions grew, the army garrisoned the area around their encampment, while Abhisit lived at an army base for his own safety and security. Soldiers swept through barriers to forcefully end the protest on May 19, 2010.

Former Deputy Prime Minister Suthep Thaugsuban, who was in charge of the special security agency set up to contain the protests, arrived with Abhisit to be charged with the same offence.

The two were greeted by DSI chief Tharit Phengdit as they walked smiling through a gauntlet of reporters into the offices of the agency, the Thai equivalent of the FBI in the United States.

The political tide has shifted several times since Thaksin's ouster. His sister Yingluck Shinawatra is now prime minister, while Abhisit leads the opposition as head of the Democrat Party. Tharit was DSI chief during Abhisit's administration, and was widely seen then as his hatchet man for aggressively prosecuting Red Shirt leaders and supporters.

Thaksin is in self-imposed exile to avoid serving a two-year jail term imposed on him for a conflict of interest conviction in 2008. Thaksin's supporters say he was unfairly convicted and would like to see him return without being jailed, while his opponents, such as Abhisit, insist that he not be let off the hook.

The case against Abhisit and Suthep is seen by many as a bargaining chip, to gain support for an amnesty that would cover many of the people charged or convicted of crimes in connection with the political battles after the coup. An amnesty to lift Thaksin's conviction would be would be more politically palatable if it covered Abhisit as well.

However, Abhisit in recent interviews has said he is willing to face justice, implying that Thaksin should take the same position.

About 50 Red Shirt demonstrators gathered peacefully outside DSI headquarters before Abhisit's arrival, seated on the ground and holding framed photos of relatives killed during the protests, as they shouted protests slogans over loudspeakers.

Several expressed the hope that the politicians would take responsibility for their actions and be placed in custody immediately after being charged.

Payao Akkhahad's daughter, Kamolkate, was a volunteer medic who was shot dead while treating injured Red Shirts who were sheltering at a temple after the army swept in.

"Her siblings and relatives have been waiting for this for a long time," said Payao, 47. "This is the first time that a person who has ordered the killing of civilian protesters will be put through legal proceedings. Even though it's late, it's better than a day that never comes at all."

About a dozen people showed up to offer flowers and moral support to Abhisit and Suthep. About 400 policemen were on the scene to maintain the peace, but had little to do.