Villagers on Thursday buried some of the 78 Muslims who died in military custody after a protest in troubled southern Thailand (search), while authorities insisted at a briefing for diplomats that the detainees were not intentionally mistreated.

Later Thursday evening, a bomb exploded outside a bar in the region, killing two people and injuring 21, police said.

Outraged Islamic leaders have warned that the deaths of the Muslims in custody could worsen sectarian violence in the south, the only Muslim-majority area in mostly Buddhist Thailand. More than 400 people have been killed in violent attacks in the area this year.

The deaths occurred after a protest Monday outside a police station in Narathiwat (searchprovince turned violent, with at least seven people killed, apparently shot by security forces. Then, as 1,300 people were rounded up and detained, 78 were suffocated or crushed to death when they were packed tightly into military trucks, officials said.

The Foreign Ministry has put the death toll from Monday's violence at 87, though it was not clear the circumstances of all the deaths.

Thousands of Muslims gathered in the province for the mass burial of 22 unidentified victims, but the crowd thinned before the bodies were brought from a military camp in neighboring Pattani province.

Scores of people, some wearing sarongs and white skull caps, watched as volunteers carried the corpses wrapped in white fabric and tarps from pickup trucks to the foot of a mass grave as night fell and Islamic leaders recited prayers.

Some residents held cloth to their noses to mask the smell of the bodies, which were gently lowered into a ditch at a rural cemetery fringed by jungle near a 17th century mosque.

Armed police and soldiers stood nearby.

Earlier Thursday, some people searched for relatives at the army camp in Pattani province, where up to 1,300 detainees were taken after Monday's riot. Most detainees were later moved to other camps in the south.

Foreign governments, including predominantly Muslim Malaysia, which borders the restive region, have expressed concern about the unrest.

At a special briefing late Thursday, Foreign Ministry Permanent Secretary Krit Garnjana-Goonchorn told diplomats from 54 countries -- including 19 ambassadors -- that "mistakes and errors of judgment were apparently made, but there was no deliberate intent, in any way, to mistreat the detainees."

Besides the 87 dead, the violence also wounded 37 people. Nine had gunshot wounds and the rest suffered bruises and dehydration. Five were in critical condition, a hospital official said.

Prime Minister Thaksin Shinawatra has defended the security forces, saying they acted appropriately in dispersing the riot. He conceded that mistakes were made in transporting detainees and appointed a committee to investigate.

Thaksin and other officials sought to blame the detainees' deaths in part on weakness due to dawn-to-dusk fasting during the Muslim holy month of Ramadan. But a government-employed forensic scientist said two or three of the detainees had broken necks.

An unsigned statement distributed by fax to government offices in Narathiwat warned: "Buddhists who want to save their lives should leave our land immediately, or we will kill one of you for every one of our brothers killed by soldiers."

Many victims of violence in the south in recent years have been security or government officials killed in drive-by shootings or small-scale bombings.

In Thursday night's fatal bombing, the explosive was left in a box in front of a beauty shop next to a bar in the town of Sungai Kolok by two men on a motorcycle who sped off as it went off, police said.

Police identified one of the dead as a Malaysian from just over the border in the state of Kelantan, while the other victim was a hostess from the bar. At least 21 people were hospitalized, mostly from Malaysia.

No one claimed responsibility for the bombing and police did not immediately name any suspects.

Earlier, a 33-year-old Buddhist man who owned a fruit orchard in Narathiwat died after being shot six times by a gunman on the back of a motorcycle.

Officials say the violence is part of a revived separatist movement that simmered in the south for decades before largely fading in the 1980s. Southern Muslims have long complained of discrimination by the central government.