Uganda's main opposition party rejected presidential election results and called for the release of its leader, Bobi Wine, who has been under what amounts to house arrest since polling day.
President Yoweri Museveni on Saturday won a sixth five-year term, extending his rule to four decades, official results show.
Uganda’s military on Sunday continued to hold top challenger Mr Wine at his home, saying troops were there to protect him.
He dismissed Mr Museveni’s victory as “cooked-up, fraudulent results” while his party urged the government to release him.
Mr Wine said on Sunday that he had proof he had won the election.
“We were leading Gen Museveni by a very large margin, so large that he could not recover,” he said by phone from his home.
“Our polling agents have proof of our victory. We have proof that the military carried out voting fraud but we cannot publish these videos because the internet is cut and because the military is chasing our polling agents.”
Mr Wine said his party, the National Unity Platform, had video evidence of the military stuffing ballot boxes, casting ballots for people and chasing voters away from polling stations.
He tweeted on Sunday that soldiers were not allowing him or his wife, Barbie, to leave their house, or even to harvest food from their garden.
“It’s now four days since the military surrounded our home and placed my wife and I under house arrest,” Mr Wine said.
“We have run out of food supplies and when my wife tried to pick food from the garden yesterday, she was blocked and assaulted by the soldiers staged in our compound.”
Mr Wine said he and his wife were concerned about the safety of his party’s polling agents and other supporters.
“We are detained at our house, while others have been abducted and are missing," he said.
"The military is conducting a massive campaign to arrest our agents. Many are on the run.”
Mr Wine said he and his supporters were pursuing a legal and peaceful challenge to Mr Museveni.
“What we are doing is moral and right," he said. "We are doing this legally and non-violently.
"So many people are paying the price for standing up for what is moral and what is right for Uganda.
"Forty-five million Ugandans are yearning for peaceful change, to redefine our country and our democracy.”
The National Unity Platform called on all Ugandans "to reject this fraud". It said: "This is a revolution and not an event. A revolution of this nature cannot be stopped by a fraudulent election."
It said its “quest for a free Uganda is on despite the current attack on free speech and association", referring to the days-long shutdown of the internet by the government.
The party urged its followers to use every “constitutionally available avenue” to pursue political change.
“As we speak now, our president [Mr Wine] is under illegal detention at his home,” opposition politician Mathias Mpuuga said at the party headquarters in Kampala.
“Perhaps his crime was to defeat Mr Museveni on the day he has selected as his crowning."
Mr Mpuuga said Mr Wine, 38, was “not allowed to leave or receive visitors at his home".
Mr Wine’s party claimed that soldiers had broken into his compound and were freely using utilities including power and water.
“We are concerned about the state in which he is,” party spokesman Joel Ssenyonyi said. “Is his house now a barracks?
“There will be a Uganda after Museveni and there will be an army that serves the interests of the country.”
Uganda’s electoral commission said Mr Museveni received 58 per cent of the vote to Mr Wine’s 34 per cent, with a voter turnout of 52 per cent.
Although Mr Museveni stays in power, at least nine of his Cabinet ministers, including the vice president, were defeated in the parliamentary elections, many to candidates from Mr Wine’s party, local media reported.
Mr Wine, a singer turned politician, posed arguably the greatest challenge to Mr Museveni, 76, since he came to power in 1986.
Calling himself the “ghetto president”, Mr Wine had strong support in Ugandan cities, where frustration with unemployment and corruption is high.
Mr Museveni dismissed the claims of vote-rigging.
"I think this may turn out to be the most cheating-free election since 1962," he said in a national address on Saturday, referring to when Uganda won independence from Britain.
The electoral commission deflected questions about how countrywide voting results were transmitted during the internet blackout by saying: “We designed our own system.”
“We did not receive any orders from above during this election,” commission chair Simon Byabakama said, adding that his team was “neither intimidated nor threatened".
Tracking the vote was further complicated by the arrests of independent monitors and the denial of accreditation to most members of the American observer mission, leading the US to cancel its monitoring of the vote.
“Uganda’s electoral process has been fundamentally flawed,” tweeted the top US diplomat for Africa, Tibor Nagy.
“The US response hinges on what the Ugandan government does now.”
The US State Department urged “independent, credible, impartial, and thorough investigations” into reports of irregularities.
It condemned “the continuing attacks on political candidates” and called for the immediate restoration of the internet and social media.
“We reiterate our intention to pursue action against those responsible for the undermining of democracy and human rights in Uganda,” the department said.
Some members of Mr Museveni's ruling party, the National Resistance Movement, were injured when soldiers tried to stop them boisterously celebrating the president's win.
Events in Uganda are also being followed by the man named by US president-elect Joe Biden to be his national security adviser.
“The news from Uganda is deeply concerning," Jake Sullivan tweeted on Sunday.
"Bobi Wine, other political figures and their supporters should not be harmed, and those who perpetrate political violence must be held accountable.
“After this flawed election, the world is watching.”