YANGON, Myanmar (AP) -- Supporters of Myanmar's opposition icon Aung San Suu Kyi erupted in euphoric cheers Sunday after her party said she won a parliamentary seat in a landmark election, setting the stage for her to take public office for the first time.
The victory, if confirmed, would mark a major milestone in the Southeast Asian nation, where the military has ruled almost exclusively for a half-century and where a new reform-minded government is seeking legitimacy and a lifting of Western sanctions.
It would also mark the biggest prize of Suu Kyi's political career, and a spectacular reversal of fortune for the 66-year-old Nobel Peace Prize laureate who the former junta had kept imprisoned in her lakeside home for the better part of two decades.
The victory claim was displayed on a digital signboard above the opposition National League for Democracy's headquarters in Myanmar's main city, Yangon, where more than 1,000 supporters began wildly shouting upon learning the news.
"We won! We won!" her supporters chanted while clapping, dancing, waving red party flags and gesturing with thumbs-up and V-for-victory signs.
Earlier, the party had claimed that Suu Kyi was ahead with 65 percent of the vote in 82 of her constituency's 129 polling stations. The party had staff and volunteers spread throughout the vast rice-farming district, who were calling in preliminary results by phone to their headquarters in Yangon.
The results must be confirmed by the official electoral commission, however, which has yet to release any outcome and may not make an official declaration for days.
The victory claim came despite allegations by her National League for Democracy party that "rampant irregularities" had taken place on voting day. Party spokesman Nyan Win said that by midday alone the party had filed more than 50 complaints to the Election Commission. He said most alleged violations concerned waxed ballot papers that made it difficult to mark votes. There were also ballot cards that lacked the Election Commission's seal, which would render them invalid.
Sunday's by-election was called to fill just 45 vacant seats in Myanmar's 664-seat national Parliament and will not change the balance of power in a new government that is nominally civilian but still heavily controlled by retired generals. Suu Kyi and other opposition candidates would have almost no say even if they win all the seats they are contesting.
But her candidacy has resurrected hope among Myanmar's downtrodden masses, who have grown up for generations under strict military rule. If Suu Kyi takes office as expected, it would symbolize a giant leap toward national reconciliation.
"She may not be able to do anything at this stage," said one voter, Go Khehtay, who cast his ballot for Suu Kyi at Wah Thin Kha, one of the dirt-poor villages in the rural constituency south of Yangon that she is vying to represent. "But one day, I believe she'll be able to bring real change."
Earlier, crowds of supporters mobbed Suu Kyi as she visited a polling station in the village after spending the night there. The tiny community of 3,000 farmers has no electricity or running water, and its near-total underdevelopment illustrates the profound challenges facing the country as it slowly emerges from 49 years of army rule.
Despite the reports of widespread irregularities, a confirmed victory by Suu Kyi could cheer Western powers and nudge them closer to easing economic sanctions they have imposed on the country for years.
Suu Kyi herself told reporters Friday that the campaigning for Sunday's vote been anything but free or fair, but that she was pressing for forward with her candidacy because it's "what our people want."
Last year, Myanmar's long-entrenched military junta handed power to a civilian government dominated by retired officers that skeptics decried as a proxy for continued military rule. But the new rulers -- who came to power in a 2010 vote that critics say was neither free nor fair -- have surprised the world with a wave of reform.
The government of President Thein Sein, himself a retired lieutenant general, has freed political prisoners, signed truces with rebel groups and opened a direct dialogue with Suu Kyi, who wields enough moral authority to greatly influence the Myanmar policy of the U.S. and other powers.
Suu Kyi's decision to endorse Thein Sein's reforms so far and run in Sunday's election represents a political gamble.
Once in parliament, she can seek to influence policy and challenge the government from within. But she also risks legitimizing a regime she has fought against for decades while gaining little true legislative power.
Suu Kyi is in a "strategic symbiosis" with some of the country's generals and ex-generals, said Maung Zarni, a Myanmar expert and a visiting fellow at the London School of Economics.
"They need her and she needs them to break the 25 years of political stalemate," Zarni said. "She holds the key for the regime's need for its international acceptance and normalization."
Sunday's poll marks the first foray into electoral politics by Suu Kyi's National League for Democracy party since winning a landslide election victory in 1990. The military annulled those results and kept Suu Kyi in detention for much of the next two decades. The party boycotted the last vote in 2010, but in January the government amended key electoral laws, paving the way for a run in this weekend's ballot.
A new reform was expected Monday when Myanmar's currency will be largely unshackled from government controls that kept the kyat at an artificially high rate for decades. The International Monetary fund says the change could lift a major constraint on growth in one of Asia's least developed countries.
Associated Press writer Aye Aye Win contributed to this report.