Opposition leader Aung San Suu Kyi said Friday that Burma's landmark weekend elections will be neither free nor fair because of widespread irregularities, but vowed to continue her candidacy for the sake of the long-repressed nation.

Suu Kyi said opposition candidates had been targeted in stone-throwing incidents, campaign posters vandalized and members of her party intimidated during the run-up to Sunday's closely-watched parliamentary byelections.

During a news conference on the lawn of her crumbling lakeside residence in Rangoon, the 66-year-old Nobel Peace Prize laureate said government officials were involved in some of the irregularities and that they go "beyond what is acceptable for democratic elections."

"Still," she said, "we are determined to go forward because we think this is what our people want."

The vote to fill several dozen vacant legislative seats comes after months of surprising reforms carried out by Burma's nominally civilian, post-junta government, including the release of political prisoners, truces with rebel groups and a dramatic easing of media censorship.

'I do not think that we can say that this election is going to be free and fair if we just look at the process that has been going on.'—Burmese opposition leader Aung San Suu Kyi

The poll is a crucial test of Burma's commitment to change, and Western nations have held out the possibility of lifting some sanctions if all goes smoothly.

In a televised speech last Sunday, President Thein Sein admitted to "unnecessary errors" in ballot lists and asked voters and politicians to respect "the decision of the people."

Country on 'reform road'

Presidential adviser Nay Zin Latt told The Associated Press on Friday that "there could be some flaws and some bumps in the process, but our leaders have publicly said that their policy is to hold a free, fair and impartial election."

What's important, he added, is that "the country is on its reform road, and is in the process of building a democratic society."

The vote is likely to mark a symbolic turning point by bringing Suu Kyi into parliament for the first time since emerging to lead the nation's struggle for democracy nearly a quarter century ago. She spent most of that time under house arrest, and her candidacy has raised hopes for a more representative government after almost 50 years of military rule. It could also set the stage for her to run for president during the next national poll in 2015.

'There could be some flaws and some bumps in the process, but our leaders have publicly said that their policy is to hold a free, fair and impartial election.'—Burmese presidential adviser Nay Zin Latt

But with parliament overwhelmingly dominated by the ruling party, and with 25 per cent of legislative seats allotted to the army, Suu Kyi and her opposition colleagues will be hard-pressed to achieve much if they are elected.

Suu Kyi said there were "many, many cases of intimidation" and acts which broke electoral laws. Her National League for Democracy party says those include election commission officials campaigning for the ruling party, and leaving eligible voters off voting lists while including the names of dead people.

Her party also alleges opponents engaged in vote-buying, and they cite inconveniences like a rule barring Suu Kyi from holding campaign rallies in stadiums.

Concern over irregularities

Suu Kyi said there were attempts to injure opposition candidates with stones or other thrown objects, and that one security guard was hospitalized.

"I do not think that we can say that this election is going to be free and fair if we just look at the process that has been going on," Suu Kyi said. "Some of the irregularities were committed by those in official positions."

Still, she said she hoped that "the courage and the resolution of people will overcome the intimidation."

The United States said Friday it has raised its concerns with authorities in Burma, also known as Myanmar, about some "irregularities" in the run-up to the vote. State Department spokesman Mark Toner said the U.S. would be closely watching the election, although he cautioned international observers now in-country would not have enough time to conduct a proper assessment of the vote.

"This is an important moment for Burma. These byelections, if seen as free and fair, will demonstrate the government's commitment to democratization," Toner said at a news conference in Washington. "This would further propel momentum in our bilateral relations."

Suu Kyi said she was confident that Thein Sein "wishes for democratic reform, but as I've always said, I have never been certain as to exactly how much support there has been behind him, particularly from the military."

The byelection will fill 45 vacant seats in Burma's 664-seat national parliament.