Thousands of Burmese civilians have crossed the border into China
recently, fleeing fighting between Burmese troops and rebels in Burma's
eastern state of Shan.
Media reports quote witnesses as saying Burmese troops have occupied the city of Laogai in Shan's Kokang region, which is largely populated by ethnic Chinese.
Residents are leaving out of fears there will be fighting between the troops and elements of a local opposition militia, the Myanmar Democratic Alliance, the MNDAA. led by Peng Jiasheng.
The group which has had a long-term ceasefire with the Burmese military recently split, with some members agreeing to join the military as part of an ethnic border-guard force.
Chinese media reports say at least 10,000 people have crossed the border into China's southern Yunnan province in the past three weeks.
Tensions in the region have been on the rise since August 8 when the Burmese government deployed troops in Kokang.
The Myanmar Peace and Democracy Front, an alliance of four ethnic groups, says the military wants to transform the Kokang armed forces into government-controlled border guards.
Some exiled Burmese activists say Burma's military leaders are trying to eliminate the threat posed armed ethnic militias ahead of next year's elections, by forcing rebel fighters into the government's army.
The government has signed ceasefire agreements with ethnic militias but relations between authorities and the militias have been volatile. Many Burmese refugees also live along Thailand's border with Burma.
Burma is home to more than 100 ethnic groups.
Some information for this report was provided by AFP and AP.