Thousands of ethnic Karen villagers have been forced to flee across the border into Thailand over the past few weeks as the Myanmar army steps up its assault on the Karen rebels.

Myanmar's army and a pro-government militia called the Democratic Karen Buddhist Army (DKBA) attacked the border region near Thailand in a final push to destroy the Karen National Union (KNU), which has been fighting for independence for the last 60 years.

Fierce combat and mortar fire has forced more than 4,000 ethnic Karen villagers to flee across the border for their safety since the beginning of June. More are arriving every day.

So far, the refugees have fled from seven villages across the Moei River in Burma, but there are more than 40 villages in the conflict zone.

"If the fighting continues, at least 8,000 more villagers will have to escape across the border or die at the hands of the soldiers," KNU general secretary Zipporah Sein said.

Some of the recent refugees are crowded into the grounds of a temple, a couple of kilometres inside Thailand, where they are healthy but lack access to basic necessities, aid workers said.

"They are in relatively good condition," Kitty McKinsey, regional spokeswoman for the United Nations High Commission for Refugees, said from Noh Bo temple near the Thai border town of Mae Sot.

"They are not emaciated, though many have walked for more than seven days to escape from the Myanmar army," she told the German Press Agency dpa. "They hurriedly left with nothing but the clothes on their back."

"We desperately need soap, toothbrushes and cooking utensils," said Ma Theingyi, a 33-year-old mother of five. "More than anything though, we need clothes for our children."

Most of the refugees are women and children. Some of the men stayed behind to look after the fields, aid workers said. Others were already in Thailand, as illegal immigrants working in foreign-owned textile factories near the border. And some are soldiers in the KNU's armed wing, the Karen National Liberation Army.

The mass exodus of Karen villagers began more than a month ago after the DKBA told the local village headman that they intended to recruit more soldiers and porters.

"We knew what that meant, all the able-bodied men would be used by the army in one way or another, and on top of that we would have to give them money and food rations," said Pa Naw Naw, 41. He fled with his wife and three children, but left his 11-year-old son behind to keep an eye on their fields and livestock.

The KNU is one of many ethnic groups in Burma that have fought the ruling military junta for autonomy. Most of the other rebel groups now have ceasefire agreements with the government. Over the past 20 years, military action, internal strife and defections have whittled away at the KNU's strength.

The Karen insurgency may now be facing its final battle.

"We will fight to the bitter end," said David Thakerbaw, a spokesman for the KNU. He has been fighting against the Myanmar army for most of his life, joining as a 14-year
-old recruit, some 60 years ago.

"We have no option but to fight on and hold on to every strip of land," he said. "We know they will continue to commit human rights abuses, seize our land and control our natural resources."

The latest army offensive began about two weeks ago with shelling in the border area and terrorizing villagers with the help of the breakaway Karen faction, the DKBA.

"There is no doubt that the junta with the help of the DKBA, are going all out to wrest control of the area along the border from the KNU," said Win Min, a Myanmar academic and military specialist.

The military campaign appears linked to the regime's planned elections next year and the proposed creation of a national border police force, to be made up of the disarmed ethnic rebel armies that have ceasefire agreements with the regime.

Most ethnic groups have rejected the junta's plans to disarm them before the elections, but the DKBA has agreed in principle to become border police.

In the border area where the KNU is active, the army has closed some 30 of its 100 military camps in recent months, in anticipation of the DKBA taking control of the area, according to the medical aid organization Free Burma Rangers.

"They want to eliminate KNU now because we have called on all Karen to boycott the elections," said Thackerbaw. "The last thing they want is for other ethnic groups to follow our lead."

Across the border in Myanmar, also called Burma, many villagers are bracing themselves for more fighting and shelling. The next few days are likely to see the army intensify the operations, a senior Thai military officer said.

"We want an end to all this fighting. All we want is to be left alone in peace, and to be able to return to our homes," said Pa Kyaw, a 30-year-old refugee at Noh Bo monastry.