Preparations are under way for the expected release of Myanmar's detained opposition leader Aung San Suu Kyi, officials said on Wednesday, after the army's proxies claimed a landslide election win.

The Nobel Peace Prize winner, who has spent most of the past two decades locked up, is due to be freed on Saturday, just days after a widely criticised election that her party boycotted.

"We haven't got any instruction from superiors for her release yet. But we are preparing security plans for November 13," a government official told AFP on condition of anonymity.

Suu Kyi's lawyers say the current period of detention started with her imprisonment on May 14 last year and they expect her to be liberated on Saturday.

Yet some fear Myanmar's military regime, headed by junta chief Senior General Than Shwe, may still find an excuse to extend Suu Kyi's sentence.

Another official, who also did not want to be named, said: "We don't have the order yet. It will be at the last minute."

Suu Kyi's detention was extended by 18 months in August last year over a bizarre incident in which an American swam uninvited to her lakeside home, where she is under house arrest, keeping her off the scene for the election.

Her lawyer said Wednesday she would hold a news conference at her party's headquarters if freed, suggesting she is likely to resist any attempt by the authorities to restrict her political activities.

"In they past they always made conditions when they released her," said Nyan Win. "But she has never accepted these."

When the softly-spoken but indomitable opposition leader was last released in 2002 she drew huge crowds wherever she went -- a reminder that years of detention had not dimmed her immense popularity.

The daughter of Myanmar's founding father General Aung San swept her National League for Democracy (NLD) to power in the country's last elections two decades ago, but the party was never allowed to take power.

Her likely release is seen by observers as an effort by the regime to deflect criticism of Sunday's election.

The NLD was disbanded after boycotting the poll -- widely dismissed by the West for being a sham with Suu Kyi sidelined. The party's decision not to participate deeply split Myanmar's opposition.

Some former NLD members left to create the National Democratic Force (NDF), which was weighing its next move after the junta-backed Union Solidarity and Development Party (USDP) said it had won 80 percent of the seats.

The largest opposition party running, the NDF appeared to have secured only about 10 percent of the more than 160 seats it contested, and accused the USDP of cheating through its collection of advance ballot.

"We will send our complaint letter to the Union Election Commission asking it to cancel the advance votes which were illegal," said party leader Khin Maung Swe.

He said it would also challenge the conduct of USDP members at polling stations.

"We are not boycotting the election nor neglecting it. The NDF will never abandon the people no matter what situation we have to face," he told AFP.

The Democratic Party, the second largest pro-democracy group, appeared not to have won a single seat in the national legislature, but chairman Thu Wai said they "cannot do anything".

"We are planning to discuss with other parties after we collect the data. We will try to work not only with the NDF but also with other parties," he said.

One quarter of the seats in parliament are already reserved for the military, which together with its political proxy looks set to have a comfortable majority for passing laws and electing the president.

A new constitution requires parliament to convene only at least once a year.

Thai officials said Wednesday that 20,000 refugees had returned to Myanmar after crossing the border into Thailand following the outbreak of fighting between ethnic minority rebels and government forces a day after the poll.

The state-run New Light of Myanmar said three civilians were killed and 20 injured, blaming "terrorists".

It said one police officer was killed and four soldiers wounded in a separate border clash.

The English-language newspaper ran little about the poll aside from a piece about China welcoming the "smooth general election".

Myanmar's Southeast Asian neighbours have also welcomed the vote as a "significant step forward", but the United Nations, the United States, Europe and Japan have criticised the poll.