YANGON, MYANMAR, MAY 27 -- A democratic opposition party whose leaders are being held by the military government took an early lead today in the first multi-party elections in 30 years in this nation, formerly called Burma.

Supporters of the National League for Democracy cheered and danced in the streets as the first official results were announced on state radio, declaring the opposition party the winner in three of the 492 races for seats in the national legislature.

The election was called by the military government, which in September 1988 crushed a nationwide uprising against military rule. More than 1,000 were killed.

The military leaders have said they will hand over power to a civilian government. But over the past 20 months the government has imprisoned and intimidated political opponents.

Today's election proceeded without any reports of violence or military shows of force. However, the government imposed a curfew on the capital and closed the polls after 10 hours of voting and four hours of counting ballots by hand.

The early election returns indicated that the league was winning by wide margins. In the capital's Seikan constituency, the party commanded 60 percent of the vote. The pro-military National Unity Party received 35 percent, official Yangon Radio said. A league spokesman said the party was confident it had won 16 seats in the capital's 61 constituencies. Preliminary indications from other major cities also suggested that voters had rejected the pro-military party.

Initial reports indicated a 60 to 70 percent voter turnout in major cities. Officials said a final tally could take up to three weeks.

Results outside the cities, where 70 percent of Myanmar's 41 million people reside, were less predictable. Some analysts speculate that the pro-military party could make a strong showing in rural areas.

The military government has detained two leaders of the National League for Democracy. Aung San Suu Kyi, daughter of independence hero Aung San, is under house arrest, and the party's general secretary Tin Oo is serving a three-year sentence on charges of sedition.

Although the government rejected requests for foreign official observers at the polls, there was no sign of interference or intimidation at Yangon voting stations visited by foreign journalists.

Some ethnic minority rebel and student dissident groups boycotted the elections. However, rebel sources in Bangkok said the groups had called off earlier plans to sabotage polling.

The 492 parliamentary seats were contested by 2,297 candidates from 93 parties, but only a half dozen of them were expected to make a significant showing.

The military government has said it will hand over power after the new legislature approves a constitution. New elections for a civilian government are held under the document's provisions.

Asked if he would allow a civilian government to run the country, junta leader Gen. Saw Maung, emerging from a polling booth in central Yangon, said, "I have already abided by my promise. I will transfer power according to the law."

The military has been in power since a 1962 coup, led by Gen. Ne Win, enforced an isolationist "Burmese Way to Socialism."