In Thailand, the mystery of who is behind months of violent attacks in the mostly Muslim south remains, but new clues are starting to emerge. Since Wednesday's deadly clashes, with a death toll of more than 100, police have captured and interrogated some militants, finding that a shadowy Islamic movement may be responsible. But drug smugglers, bandits and terrorists are still under suspicion.

A web site bearing the name of the Pattani United Liberation Organization, or PULO, warns tourists may find themselves in danger if they visit Thailand's Muslim-dominated south.

Australia and the United States have advised citizens to exercise caution about visiting the region, and Thai tourism officials say they are bracing for at least a short-term decline in the industry.

On Wednesday, more than 100 people were killed in clashes between militants and Thai security forces in the south.

Police say the militants shouted Islamic slogans as they attacked police and army outposts. But there is conflicting information about whether or not Wednesday's clashes and other violence since January is the work of an organized movement.

Thai Prime Minister Thaksin Shinawatra says southern militants are linked to drug traffickers and corrupt politicians. The Thai Public Health minister says several of the insurgents had methamphetamines and other illegal drugs in their bloodstream.

But an Islamic cleric in Thai custody refuted the government statements Friday. As police escorted him in handcuffs, the suspect told reporters the militants were fighting for a separate Islamic state.

Those comments were the first time an Islamic leader in southern Thailand has explicitly stated aims for militant action. Professor Ron May is an expert on Muslim separatist movements in Southeast Asia at Australia National University. He says Thailand's Islamist movement is partially homegrown, but probably receives help from international groups like Jemaah Islamiyah, or J.I.

"I don't think there's much doubt that J.I. and other groups have been operating in Southern Thailand, and as the Army has moved in, there have been increasing clashes," he said.

Panitan Wattanayagorn is with Thailand's Chulalongkorn University's Institute of Security and International Studies. He says there are three main groups who are linked to violence attacks in the South.

"The first group, of course, is the individuals who are running the training camps - the individuals who are involved in the fundamentalist and radicalist movements in the south. The second group is the leaders of organized crime groups? The last group is officers at the higher level-at the national level-at that level certain members of parliament, certain key politicians have been implicated. Some have been arrested," he said.

PULO-whose website now appears to be carrying the latest tourist warning was at its strongest in the late 1970s. The separatist movement numbered about 20,000 fighters, and sought independence from predominantly Buddhist Thailand.

But Professor Ron May says the movement dwindled through the 80s and 90s. "But with recent events, and the military increasingly active down there, those feelings of cultural separateness will emerge again," he said.

It remains to be seen whether the recent violence in southern Thailand is the product of a genuine religious and ethnic uprising or whether it is just criminal activity dressing itself up as Islamist fervor. Many analysts say the real situation is probably some of both.

In the meantime, the Thai government is under pressure to provide answers about the violence. Perayot Rahimulla, of Pattani University in southern Thailand, says failing to do so will cause more fear and uncertainty.

"It is the responsibility of the government to find out who was behind (this), to answer which group, the separatist group or the other (another) group. We must have clear evidence about this," he said.

In the meantime, human rights groups and neighboring Malaysia are criticizing Thailand for firing first, and asking questions later. They say Thai Army and police personnel have used excessive force to bring the southern uprising under control since declaring martial law in the region more than three months ago.