Aung San Suu Kyi's ruling party swept to a landslide win in Myanmar's election, official results showed Friday, in a poll disputed by the military-aligned opposition and criticised by rights groups.

Her National League for Democracy (NLD) had already declared the victory based on its own tallies, prompting street celebrations by supporters.

But official figures were still coming in five days after the ballot, only the second such polls since the nation emerged from outright military rule in 2011.

Results announced by the election commission on Friday evening showed the NLD had won 396 seats —- more than 60 percent of parliament, even taking into account the quarter of seats reserved for the military under the constitution.

On the 10th anniversary of Suu Kyi's release from house arrest under the junta, her party defied many forecasts by bettering its 2015 victory, despite widespread disillusionment in many ethnic-minority areas.

"People clearly realised the need for the NLD to get enough votes to form a government on their own," NLD spokesman Myo Nyunt told AFP, adding this would help "minimise political conflict".

The military-aligned opposition Union Solidarity and Development Party (USDP) has been trounced across the country, winning just 30 seats by Friday evening with only three seats left to report.

The party alleges the vote was neither free nor fair and is demanding that the Union Election Commission (UEC) step down and polls be re-run.

Yangon-based analyst Khin Zaw Win warned the coming months would be messy, adding the situation was a consequence of the UEC being filled with "yes-men and incompetents".

Under the constitution, the government appoints all commission members.

But even if some results were overturned, "the NLD landslide is so large that they wouldn't alter the overall outcome", said Richard Horsey from the International Crisis Group.

- Fears of violence -

Japan, India and Singapore have already congratulated Suu Kyi and her party.

Observers widely concluded that voting took place smoothly on the day, despite forecasts of a low turnout due to a recent surge of coronavirus cases.

But they condemned what they described as the election commission's lack of transparency and its cancellation of the polls across many ethnic-minority areas -- ostensibly for security reasons.

The move left 1.5 million voters disenfranchised, sparking grievances in already restive areas that the playing field had been tilted in favour of the NLD.

The NLD wrote Thursday to all ethnic-minority political parties, promising it would "prioritise" their wishes.

But some will conclude the electoral process does not work for them and choose "political insurrection or insurgency instead", warned Horsey.

Tension is particularly high in western Rakhine state, where fighting between ethnic Rakhine militant group the Arakan Army (AA) and the military has already displaced 200,000.

In unprecedented communication between the foes, the AA requested the army and government hold by-elections as soon as possible in areas where the vote had been cancelled -- a statement welcomed by the military.

Rights groups also condemned Sunday's vote, which left virtually all Rohingya Muslims disenfranchised, either languishing in Bangladeshi refugee camps or stripped of citizenship in Myanmar.

Even though Suu Kyi's international reputation was badly hurt over the Rohingya crisis -- for which the country now faces charges of genocide -- she remains widely revered within Myanmar.

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© Agence France-Presse