(Adds details, state media report)
MAE SOT, Thailand, June 18 (Reuters) - Myanmar government forces captured three Karen rebel positions on Thursday in the latest fighting that has forced thousands of refugees to flee into neighbouring Thailand, commanders said.
The army and their Karen allies were also threatening two bases of the Karen National Union (KNU), the largest rebel group in the eastern former Burma.
"We captured 3 small KNU positions and are closing in on two main bases," said Captain Kha Koe of the Democratic Karen Buddhist Army (DKBA), which joined government troops in an offensive against the KNU on June 3.
There were no confirmed reports of casualties.
Earlier on Thursday, KNU Commander Kyaw Ny said his fighters were preparing to abandon their 7th brigade base to avoid unnecessary loss of life.
"It is a tactical redeployment. We also do not want to kill our fellow Karens in this battle," he told reporters by telephone.
Thai army officials say some 3,000 Karen refugees have fled across the border into Thailand since the fighting began. The U.N. refugee agency has said it is working with the Thai government to assist the refugees.
Myanmar’s state-controlled media said on Thursday those who fled to Thailand were "insurgents" from several KNU units.
The KNU has been fighting for autonomy in the hills of eastern Myanmar for the last 60 years, one of the world’s oldest insurgencies.
Rebel leaders say the latest offensive is part of the military regime’s campaign to eliminate all opposition ahead of promised multi-party elections in 2010.
The trial of Myanmar opposition leader Aung San Suu Kyi, who faces up to five years in jail if convicted of violating her house arrest, resumes next week.
Critics say the trial is aimed at keeping the Nobel laureate and National League for Democracy (NLD) leader in detention ahead of next year’s polls.
The KNU are one of a handful of rebel militias not to have signed a ceasefire with the military junta.
In February last year, KNU leader Mahn Sha Lar Phan was shot dead at his home in a Thai border town in an assassination blamed on the regime and its Karen allies.
Myanmar has been under military rule of one form or another since 1962, during which time it has been riven by dozens of ethnic guerrilla wars, funded in part by revenues from opium sales from the notorious "Golden Triangle".
(Reporting by Somjit Rungjumratrussamee; Writing by Kittipong Soonprasert; Editing by Darren Schuettler)