Former Thai prime minister Abhisit Vejjajiva has been charged with murder, his party says, over a civilian's death during a crackdown on anti-government rallies two years ago.
Abhisit and his then-deputy Suthep Thaugsuban were formally charged on Thursday at Bangkok's Department of Special Investigation (DSI), making them the first officials to face a court over Thailand's worst political violence in decades.
"The DSI has charged Abhisit and Suthep on section 288, which is murder. They both denied the charge," senior Democrat Party lawmaker Thavorn Senniem told AFP.
Hundreds of riot police flanked the building, as about 20 supporters carrying roses and dozens of protesters holding pictures of those killed in the unrest watched the former leader arrive.
About 90 people died and nearly 1900 were wounded in a series of street clashes between "Red Shirt" demonstrators and security forces, which culminated in a deadly army operation in May 2010 to break up the protest.
The charge against Abhisit, who was prime minister at the time, relates to the fatal shooting of taxi driver Phan Kamkong.
DSI chief Tarit Pengdith announced the move last Thursday and said it was prompted by a court's ruling in September that Phan was shot by troops - the first completed inquest into the bloodshed.
Abhisit dismissed the case against him as "political" last week, saying he had no choice but to take tough action.
He said he would accept trial rather than "bargain" over a proposal by his political rivals in government for a wide-ranging amnesty plan that many believe could allow the return of the Reds' hero, ousted former premier Thaksin Shinawatra.
But experts believe British-born Abhisit is unlikely to face jail because of his close ties to the Thai establishment.
A separate terrorism case against 24 Red Shirt leaders, including five current MPs, for their part in the rallies was again postponed on Thursday after two witnesses failed to turn up.
The Red Shirts were demanding immediate elections in their 2010 protest.
They accused Abhisit's government of being undemocratic because it took office in 2008 through a parliamentary vote after a court stripped Thaksin's allies of power.
Polls in 2011 brought Thaksin's Red Shirt-backed Puea Thai party to power with his sister Yingluck as premier, sweeping Abhisit into opposition.
Support from the Thai elite means Abhisit is "unlikely" to go to prison, said Thitinan Pongsudhirak of Chulalongkorn University, adding that the former premier "has a sense of political invincibility".
He told AFP that Abhisit's arraignment was part of a "political tit-for-tat", with prosecutions against both sides, but said it still could deter the use of force against demonstrators in the future.
"It is a very important charge, because it means that the sense of impunity is being challenged," he told AFP.
The DSI said earlier on Thursday that after hearing the charges Abhisit and Suthep would be released without bail because they were prominent figures.
Tarit told reporters at DSI headquarters that it was "very awkward" for him to file the charges against the pair because of their position in society and since he himself had served on the official body that oversaw the crackdown in 2010.