Officials say most of the victims died after they were arrested, many suffocating as hundreds were crammed into trucks and driven away.
They had been taking part in a demonstration in the province of Narathiwat against the detention of six Muslims accused of supplying weapons to insurgents.
The secretary general of the World Muslim Congress, Raja Muhammad Zafarul Haq, has called for justice to be served.
"I think it's a case of gross violation of human rights. It pained me to know that they were surrounded, they were arrested, they were put in the police vehicle and then they suffocated," she said.
"There should be an inquiry and those responsible must be punished."
By Just Us 27 October 04
