A National League for Democracy spokesman said it expected to win about 70% of seats.
Aung San Suu Kyi’s party heading for landslide victory in historic elections.
The 70-year-old former political prisoner has indicated and leader of the National League for democracy appeared in front of supporters, smiling from a balcony.
In an apparent indication of success the Associated Press said she told the crowds “I think you all have the idea of the results,” but cautioned, “It is still a bit early to congratulate our candidates who will be the winners.”
Official results are yet to be declared in the freest, most widespread election in the country since 1990.
Then the NLD won a huge majority which was annulled by the military junta. Suu Kyi then spent the majority of the intervening years under house arrest.
The election commission has begun to announce constituency-by-constituency results from Sunday’s poll.
All of the first 12 announced were won by Suu Kyi’s National League of Democracy (NLD). However hundreds are still to be declared.
Although the election appears to have dealt a decisive defeat to the USDP, a period of uncertainty still looms over the country because it is not clear how Suu Kyi will share power with the still-dominant military.
The military-drafted constitution guarantees one-quarter of parliament’s seats to unelected members of the armed forces.
Ms Suu Kyi cannot be president herself as the constitution bars candidates with foreign spouses or children. Her two sons hold British passports.