Hiro Muramoto, a Japanese photographer for Thomson Reuters on assignment to Thailand from his usual base in Tokyo, was shot and killed during the riots, said the press director of the Metropolitan Hospital, Pichaya Nakwatchara.

More than 680 people were injured in the melee, said Deputy Bangkok Governor Malinee Sukavejworakit.

Most of the injuries were minor due to the effects of the tear gas and rubber bullets used during clashes between red shirt protesters and soldiers throughout the day. But dozens were seriously injured by gunshots, as well as M67 and M79 grenades during the clashes at Khok Wua as the troops closed in on the red shirts' main stage at Phan Fa Bridge.

Prime Minister Abhisit Vejjajiva later said the army had halted its operation. Shortly before midnight, he went on national television to express his "regret" to the families of the victims and insist the troops involved would only have fired live rounds "into the air and in self-defence".

An army spokesman, Col Sansern Kaewkamnerd, earlier announced that the security forces were pulling back, and accused some of the protesters of using "real bullets and grenades".