Intensified fighting between Myanmar's military and pro- democracy forces has forced thousands of people to flee to neighboring Thailand.

Myanmar independent media says pro-democracy fighters attacked bases of military-backed forces on Wednesday in the southeastern state Karen.

The military reportedly retaliated by bombing a village with helicopters. Thai local authorities say about 4,000 people have fled across the border into Thailand.

The clashes come after the leader of Myanmar's junta called pro-democracy groups "terrorists" last week at a military parade. Min Aung Hlaing vowed no let-up in the fight against them.

The United Nations estimates security forces have killed nearly 3,000 civilians. One million people have fled their homes in Myanmar since the military seized power there two years ago.