Uganda's President Yoweri Museveni has taken a commanding lead in Thursday's presidential election - well ahead of his main challenger Bobi Wine, whose party has already questioned the credibility of the results.

Figures so far give Museveni 74% of the vote, with Wine on 23%, based on returns from 81% of polling stations.

Wine's party said on social media that a helicopter had landed in the grounds of his house in the capital, Kampala, and "forcibly taken him away to an unknown destination".

The son of the opposition leader said both his parents have been seized by the military, but difficulty accessing the internet in the country has made it difficult to verify this claim.

The local police told the BBC they were not aware of the incident.

Earlier, Wine said he had been placed under house arrest, with security forces surrounding his home, after he alleged fraud had taken place in Thursday's election.

At that stage, police spokesman Kituuma Rusoke told local broadcaster NBS that as a presidential contestant, Wine was "a person of interest", adding that the heavy security deployment around his home was for his own security.

Some local journalists said security forces had blocked them from accessing the opposition leader's home in Kampala's Magere area.

Wine told his supporters to ignore the "fake results" that have been announced, saying the authorities have been "stealing the vote". He did not provide any evidence to back up his claim and the authorities have not responded to his allegations.

Late on Thursday, at least seven opposition supporters were killed in disputed circumstances in Butambala, about 55km (35 miles) south-west of the capital.

The internet shutdown imposed earlier in the week means news of the violence only emerged on Friday.

MP Muwanga Kivumbi, from Wine's National Unity Platform (NUP) party, told the AFP news agency that soldiers and police fired tear gas and then live bullets at hundreds of people who were following early results announcements at his home.

"Ten were killed inside my house," he said.

Human rights activist Agather Atuhaire confirmed this account to the Reuters news agency.

However, local police spokesperson Lydia Tumushabe disputes this, maintaining police fired in self-defence after "a group of NUP goons" had attacked a police station and planned to overrun a tallying centre.

She told Reuters they were carrying machetes, axes and boxes of matches and said at least seven people had been killed.

Later on Friday, the US embassy issued an alert to its citizens because of reports the security forces were "using tear gas and firing into the air to disperse gatherings".

Following the 2021 election, in which he garnered 35% of the vote, Wine was confined to his home for several days by security forces.

Electoral chief Simon Byabakama said on Friday that the vote counting had not been affected by the internet blackout as the commission was using a "private system" to transmit results from districts to the national tally centre.

Asked about the timing of the final results announcement, Byabakama said: "We are on course to announce the winner of the presidential election within 48 hours. Before 5 PM [14:00 GMT] tomorrow, we shall have the final results."

Thursday's election followed an often violent campaign, with President Museveni, 81, seeking a seventh term in office. He first took power as a rebel leader in 1986.

Wine, a 43-year-old pop star-turned-politician, who says he represents the youth in a country where most of the population is aged under 30, has promised to tackle corruption and impose sweeping reforms, while Museveni argues he is the sole guarantor of stability and progress in Uganda.

Last week, the United Nation's Human Rights Office said that the election would be marked by "widespread repression and intimidation".

During Thursday's vote, voting was delayed by up to four hours in many polling stations around the country as ballot boxes were slow to arrive and biometric machines, used to verify voters' identity, did not work properly.

Some have linked the problems to the network outage.

Although there are six other candidates, the presidential poll is a two-horse race between Museveni and Wine.

The campaign period was marred by the disruption of opposition activities - security forces have been accused of assaulting and detaining Wine's supporters.

Rusoke, the police spokesperson, dismissed these complaints, accusing opposition supporters of being disruptive.

Internet access was suspended on Tuesday, with Uganda's Communications Commission saying the blackout was necessary to prevent misinformation, fraud and the incitement of violence - a move condemned by the UN human rights office as "deeply worrying".