The Thai premier, Thaksin Shinawatra, has told parliament that an inquiry team would investigate the deaths of 78 Muslims who died in military custody after police and troops broke up a violent demonstration.
Originally six people were reported dead and 1,300 arrested after police opened fire during a riot outside a police station on Monday.
But officials now say an additional 78 protestors died, crushed and suffocated to death, during a five-hour ride to an army base. The Justice Ministry said the detainees, who were stripped semi-naked after their arrest, were found piled on top of each other in the back of trucks.
Mr Shinawatra, speaking before the announcement of the 78 deaths, said the protestors were weak because of fasting during the holy month of Ramadam.
"It is normal that their bodies couldn't handle it. It is not about someone attacking them," he said.
The huge leap in the toll, and the manner of the deaths, are bound to add tension in the Kingdom's troubled southern region. One local Muslim scholar described the incident as a massacre and compared the deaths to gassing of victims.
Malaysian Prime Minister Abdullah Ahmad Badawi expressed concern about the deaths and urged Thailand to take firm action to resolve the conflict.
The protests were sparked by the arrest of six Muslim men accused of smuggling guns to rebels. The insurgency in the Muslim-majority southern Thailand has left over 400 people dead.
Human rights groups have accused the Thai authorities of heavy-handed tactics, including the storming of a mosque in April that left 32 Muslim militants dead.