One person has been killed and at least six wounded in an explosion in southern Thailand Friday. The bombing is the latest of almost daily attacks in the south that have killed more than five hundred people in the past year. The bomb was hidden on a motorcycle outside a bank in the city of Sungai Kolok, which lies along Thailand's border with Malaysia. Authorities say the bomb exploded as a military truck parked next to a market that is popular with soldiers in the area. They say, however, that most of the victims were civilians. Sungai Kolok is a popular entertainment center for Malaysian tourists. It was the scene of two attacks earlier this year that killed several people and wounded scores of others. On Thursday teachers suspended classes at hundreds of southern schools after two teachers were killed two days before in separate attacks. The teachers say they will boycott classes until the government improves security. More than five hundred people have died in attacks in Thailand's predominantly Muslim south since the violence began in January of last year. Authorities have warned they expect the violence to intensify as the anniversary approaches. An expert on the south at Bangkok's Chulalongkorn University, Panitan Wattanayagorn, says evidence increasingly indicates that several different groups are behind the violence. "There are loosely organized groups, ranging from the separatist movement to the extremist fundamentalist groups, combined with the transnational crime groups," he said. Mr. Panitan says as a result the government is confronting what he calls a new phenomenon of multiple problems coming from multiple sources. The government's efforts to stem the violence and find the perpetrators have angered the general population in the predominantly Muslim region, which sees the tactics as heavy handed. The crackdown has included the arrest of scores of Muslim leaders and has led to a climate of fear and mistrust of the central government of mostly Buddhist Thailand. The violence intensified after 85 mostly Muslim men died following a demonstration in Narathiwat province several weeks ago. Most of them suffocated while being transported in military trucks to detention centers. An independent commission investigating the incident says several high-ranking officers are to blame for the deaths. Thai Prime Minister Thaksin Shinawatra pledged to punish those responsible, before a meeting with the commission on Friday.