Opposition leaders Saturday formed a united front and urged citizens to join a peaceful struggle against the military government, which acknowledged killing about 250 civilians last week.

It was the first formal attempt to group under one banner the millions of students, Buddhist monks, government workers, professionals and others who took to the streets nationwide in the past two months to demand freedom.In another development, a spokesman for Burma's strongest ethnic rebel group said about 90 students who demonstrated against the government fled to his group's base camps and said they may get military training.

Em Marta, spokesman for the Karen National Union, said in Bangkok that about 200 more students were on their way to the bases along the Thai-Burmese border, including a key training camp at Thay Baw Bo.

If true, it would be the first major linkup between the rebels and pro-democracy forces. Opposition leaders earlier denied links with the rebels.

A joint statement from opposition leaders announced the formation of the National United Front for Democracy.

"The basic objective of this organization is to achieve a genuinely democratic government," said the statement by Aung Gyi, Tin Oo and Aung San Suu Kyi. "The spontaneous people's struggle for democracy, starting from the students' struggles, has developed into a national movement."

The statement did not spell out a specific strategy. The main anti-government activity is a general strike that began Aug. 8 and paralyzed the government administration.

Once a close associate of long-time strongman Ne Win, former Brig. Gen. Aung Gyi, 70, later criticized the leader's rigid political and economic policies and was recently jailed for a month..

Aung San Suu Kyi, 42, is the daughter of the late Aung San, the revered hero of Burmese independence.

Tin Oo, 61, was removed as defense and army chief in 1976 by Ne Win, and was later jailed in connection with an alleged anti-goverment plot.

The three opposition figures previously had problems cooperating. But analysts said they were pressed to unite by the bloody crackdown on dissent following the coup by military commander Gen. Saw Maung one week ago.

Saw Maung on Sunday overthrew civilian President Maung Maung, who made a series of concessions to the protesters, including the promise of the first multiparty elections since 1960.