KAMPALA: Uganda’s electoral commission says longtime President Yoweri Museveni has won a sixth term while top opposition challenger Bobi Wine alleges rigging and officials struggle to explain how polling results were compiled amid an internet blackout.

In a generational clash widely watched across the African continent, with a booming young population and a host of aging leaders, the 38-year-old singer-turned-lawmaker Wine posed arguably the greatest challenge yet to Museveni. He had strong support in urban centers where frustration with unemployment and corruption is high.

The electoral commission said Museveni received 58% of ballots and Wine 34%, and voter turnout was 52%.

The top United States diplomat to Africa has called the electoral process “fundamentally flawed.”

Thursday’s vote followed the East African country’s worst pre-election violence since the 76-year-old Museveni took office in 1986. Wine and other opposition candidates were often harassed, and more than 50 people were killed when security forces put down riots in November over Wine’s arrest. Wine petitioned the International Criminal Court this month over alleged torture and other abuses by security forces.

While the president holds on to power, at least 15 of his Cabinet ministers, including the vice president, were voted out, with many losing to candidates from Wine’s party, local media reported.

Wine claimed victory Friday, asserting that he had video evidence of vote-rigging and saying “every legal option is on the table” to challenge the official election results, including peaceful protests. Candidates can challenge election results at the Supreme Court.

Hours later, he tweeted that the military had entered his home compound and “we are in serious trouble,” which a military spokeswoman denied. Wine, whose real name is Kyagulanyi Ssentamu, was roughed up and arrested several times while campaigning but was never convicted, and eventually he campaigned wearing a flak jacket and said he feared for his life.

A heavy presence of security forces remained around his home, where he has said he was alone with his wife and a single security guard.

Uganda’s electoral commission has said Wine should prove his allegations of rigging, and it has deflected questions about how countrywide voting results were transmitted during the internet blackout by saying “we designed our own system.” It could not explain how it worked.

Monitoring of the vote was further complicated by the arrests of independent monitors and the denial of accreditation to so many members of the US observer mission that the US called it off. Another major observer, the European Union, said its offer to deploy electoral experts “was not taken up.”

“Uganda’s electoral process has been fundamentally flawed,” the top US diplomat for Africa, Tibor Nagy, tweeted Saturday, calling for the immediate and full restoration of internet access and warning that “the U.S. response hinges on what the Ugandan government does now.”

Museveni, once praised as part of a new generation of African leaders, still has support among some in Uganda for bringing stability. A longtime US security ally, he once criticized African leaders who refused to step aside but has since overseen the removal of term limits and an age limit on the presidency.

The head of the African Union observer team, Samuel Azuu Fonkam, told reporters he could not say whether the election had been free and fair, noting the “limited” AU mission which largely focused on the capital, Kampala. Asked about Wine’s allegations of rigging, he said he could not “speak about things we did not see or observe.”

The East African Community observer team in its preliminary statement noted issues including “disproportionate use of force in some instances” by security forces, the internet shutdown, some late-opening polling stations and isolated cases of failure in biometric kits to verify voters. But it called the vote largely peaceful and said it “demonstrated the level of maturity expected of a democracy.”

Uganda’s elections are often marred by allegations of fraud and abuses by security forces. The previous election saw sporadic post-election riots.