Thailand launched an operation Monday morning to close a refugee camp and send some 4,000 ethnic Hmong back to Laos, despite concerns about their safety.

Thai soldiers head to a refugee camp in Phetchabun province early Monday as an operation gets underway to expel about 4,000 ethnic Hmong back to Laos. (Sakchai Lalit/Associated Press)Col. Thana Charuwat, the Thai army's field co-ordinator for the operation, said it began at 5:30 a.m. local time and involved 5,000 troops.

He said the soldiers were unarmed, but equipped with shields and batons, which he described as meeting international standards for dealing with such situations, where people are being moved back against their will.

Many of the Hmong claim they face persecution in their homeland because of its communist government's alleged antagonism toward them.

Hmong hill tribe people fought on the side of a pro-American government during the Vietnam War, but Lao communist forces — known in the West as the Pathet Lao — emerged triumphant in 1975.

Thailand claims most of the Hmong at the camp have no legitimate claim to refugee status but are simply economic migrants who have entered the country illegally.

Thana said the army hoped to complete the operation within 24 hours. He said the Hmong would be taken to a nearby staging area where they would be put on buses that would take them to the Thai border town of Nong Khai, and then across to Laos, with their destination being the Paksane district in the central province of Bolikhamsai.

Sunai Phasuk, a Thai representative for the New York-based group Human Rights Watch, said mobile phone signals inside the camp had been jammed so nobody could call out.

Human rights groups fear that the expulsion could turn violent, with the Hmong resisting the deportation, as they have during smaller-scale repatriations.

"It never happens smoothly," Sunai said. "If the Hmong resist it and there is an eruption of violence, the army may react in full force."

Thai government spokesman Panitan Wattanayagorn said earlier that Bangkok has secured an agreement with Laos to repatriate the group before the end of the year.

Laos has in the past denied the Hmong are Lao citizens, describing them as Thailand's problem.