Prime Minister Abdullah Ahmad Badawi warned his Thai counterpart that the death of 84 Muslim protesters in southern Thailand could spark more bloodshed.

Abdullah, whose mainly Muslim country borders the troubled region, said he had spoken by telephone to Thai Prime Minister Thaksin Shinawatra to express Malaysia's concern about the deaths after a clash between demonstrators and security forces.

"I told him we are concerned about the developments and are watching very closely what is happening," Abdullah told a news conference.

"I also expressed my feelings that in the (Muslim holy) month of Ramadan, incidents of this nature can bring a lot of unhappiness and create anger and animosity among members of the community.

"We hope he will be able to manage the situation without allowing the violence to spread. It is important he manages it."

Most of the deaths occurred after troops broke up a violent protest on Monday and bundled some 1,300 detainees into trucks. They were left piled on top of each other in the trucks for at least six hours, leaving 78 dead - mainly from suffocation.

Thaksin has announced an inquiry into the deaths but Abdullah urged him also to consult Muslim leaders in the south.

"He must also speak to leaders of southern Thailand to seek their support so that violence does not continue," he said.

Thaksin had given an assurance that he would do his best to prevent an escalation of violence, Abdullah said.

PAS to hold protest

The opposition Islamic Party (PAS), whose stronghold in northern Malaysia adjoins Thailand's south, described the deaths as "a holocaust of the modern era".

"Since there are many Malaysians who have relatives on the Thai side, we fear the violence could spill across to Malaysia if the Thai military does not exercise restraint," PAS central committee member Hatta Ramli told AFP.

He said PAS members were "shocked by the massacre" and would stage a protest outside the Thai embassy on Friday.

The independent Malaysian Human Rights Commission warned that if the Thai government did not end the violence in the south, it could be viewed as ethnic cleansing by some people and exploited by extremist groups.

Malaysia has put its border police on alert and warned citizens against crossing into southern Thailand, a popular destination for tourism and shopping.

Abdullah's government has pointed to poverty among Muslims in southern Thailand as one of the causes of unrest, and has offered to help with the region's economic development.

Abdullah met Thaksin earlier this month to flesh out development plans for the three southernmost Thai provinces.