Myanmar's military unleashed airstrikes and heavy artillery on a small town controlled by ethnic guerrillas, sending hundreds of people fleeing across a river into Thailand, local officials and residents said Friday.

Government forces targeted Lay Kay Kaw, a small town near the Thai border that is controlled by the Karen guerrillas who are seeking greater autonomy from the central government. Fighting has intensified since February, when the military seized power from the elected government of Aung San Suu Kyi, and guerrillas offered refuge to opponents of the army.

The most recent clashes were triggered by a raid last week by government soldiers on Lay Kay Kaw.

Independent Myanmar media reported that government troops seized 30-60 people associated with the organized opposition to the military government, including at least one elected lawmaker from Suu Kyi's National League for Democracy party.

The sounds of gunfire, bombing and fighter jets could be heard on the Thai side of the border, where houses shook from detonations.

Last week, some 2,500 villagers also fled the fighting into Thailand's Mae Sot district.

There were no immediate reports of casualties.

Aye Lwin, a member of the Lay Kay Kaw town administration, told The Associated Press that two military aircraft bombed a location near Lay Kay Kaw. The airstrikes were followed by artillery fire from army bases starting on Thursday evening, he said.

The airstrikes took place three days after the Karen guerrillas called on the United Nations to impose a no-fly zone over Lay Kay Kaw to protect civilians.