The afternoon bombing on an area on the Salween River in Karen State's Mutraw district killed two Karen guerrillas and wounded many more, said a member of the Free Burma Rangers, which delivers medical assistance to villagers. The group's member spoke on condition of anonymity to ensure his security.

The air attacks may have been retaliation for the Karen National Liberation Army, the armed wing of the KNU, attacking and capturing a government military outpost on Saturday morning.

About 3,000 villagers from territory in eastern Myanmar controlled by the Karen ethnic minority fled across the border to Thailand on Sunday after Myanmar military aircraft dropped bombs on a Karen guerrilla position, according to workers for two humanitarian relief agencies.

The afternoon bombing on an area on the Salween River in Karen State's Mutraw district killed two Karen guerrillas and wounded many more, said a member of the Free Burma Rangers, which delivers medical assistance to villagers. The group's member spoke on condition of anonymity to ensure his security.

Hsa Moo of the Karen Peace Support Network, a civil society group, said the area near the guerrilla position was settled by about 3,000 people, most of whom are believed to have fled across the nearby border to Thailand after the attack.

Thai authorities with knowledge of the situation could not be reached Sunday.

The tension at the frontier comes as the leaders of the resistance to last month's coup that toppled Myanmar's elected govenment are seeking to have the Karen and other ethnic groups band together and join them as allies, which would add an armed element to their struggle.

The Karen National Union, or KNU, the leading political body for the Karen minority, is one of more than a dozen ethnic organizations that have been fighting for decades to gain more autonomy from Myanmar's central government.

So far the ethnic armed groups have only committed to providing protection to protesters in the areas they control.

It was the second day in a row that Myanmar forces bombed territory controlled by the KNU.

On Saturday night, two Myanmar military planes twice bombed Deh Bu Noh village in Mutraw district, which houses the district administrative office of the KNU. There are about 10,000 people settled in the area around the village, said Hsa Moo

Initial reports said two villagers were killed in Saturday's bombings, but Hsa Moo said Sunday that the death toll was at least nine, with additional people wounded, according to residents she contacted by phone.

She said she was told two homes were burned to the ground and others suffered lesser damage. Some villagers have bunkers to protect themselves, but an unclear number of others fled into the jungle for safety after the attacks and had not returned Sunday, she added.

The air attacks may have been retaliation for the Karen National Liberation Army, the armed wing of the KNU, attacking and capturing a government military outpost on Saturday morning.

According to Thoolei News, an online site that carries official information from the KNU, eight government soldiers including a second lieutenant were captured in the attack and 10 killed, including a lieutenant colonel who was a deputy battalion commander. The report said one Karen guerrillas had been killed.