BANGKOK - Investigations are under way into the bomb that exploded in southern Thailand Thursday, killing at least six and wounding more than 40 people.

Thai Prime Minister Thaksin Shinawatra has blamed relatives of wanted insurgent leaders for the bomb that exploded in a hotel parking lot. No one has claimed responsibility for the bomb, which had been placed in a stolen vehicle.

Thailand's mostly Muslim southern provinces of Yala, Narathiwat and Pattani have been wracked by violence that has left more than 600 people dead in the past year.

Thursday's bombing, the latest in a recent series, came as newly re-elected Mr. Thaksin ended a two-day visit to the provinces. The trip was billed as an effort to resolve the violence that has escalated despite the deployment of up to 20,000 troops to the region.

Mr. Thaksin said he would cut development funds to villages suspected of supporting militants and lay siege to them if withholding funds failed to end that support.

The government has described its policy as "iron fists" and "velvet gloves." Spokesman Jakrapob Penkair said the strategy remains unchanged. "The main strategy of striking a balance between 'iron fists' and 'velvet gloves' will not change," he said, "but we would dig deeper into details and information of why they are advancing quite heavily at this time."

Human rights groups and local Muslim teachers have urged the government to adopt a more moderate stance, criticizing the move to withhold development funds. But Mr. Jakrapob said the measure is only short-term.

"We are going to withhold some funds on the very clear criteria in order to make it as immediate and short-range measure to cope with the problem," he said. "Withholding funds is not a long-term strategy."

Kraisak Choonhavan, a member of the Thai Senate's foreign relations committee, said the growing violence indicates the government's policies have failed, and the strategy of withholding funds will backfire. "By punishing the entire communities has caused more resistance and as you see the answer to this is deadlier bombs and more death and destruction," he said.

Over the past year the government has sought to win over local communities with massive spending programs backed by military operations, but human rights groups have accused the authorities of abuses, saying dozens of people having been killed or have disappeared.

Mr. Kraisak said most communities were seeking justice. "They want justice from the military and from the police and to stop kidnapping and murdering them," he said. "It's justice that they want and not separation - not autonomy, neither [sic] - just simple justice; but now maybe that's too late."