Uganda's long-time leader Yoweri Museveni held a commanding lead in a presidential election according to partial results on Saturday morning, with final results expected later in the day, though his main rival Bobi Wine alleged widespread fraud.

With ballots from 86% of polling stations counted, Museveni had won 5.3 million, or 58.8%, while main opposition candidate Wine had 3.1 million votes (34.6%), the electoral commission said just after 9 a.m. (0600 GMT).

The government ordered the internet to be shut down the day before voting on Thursday, and the blackout was still in place.

Wine, 38, had galvanised young Ugandans with his calls for political change after 35 years of Museveni, 76, ruling the country.

The run-up to the election was more violent than in previous polls. Security forces cracked down on opposition candidates and their supporters during the campaign, and more than 50 people died in protests in November on one of the multiple occasions when Wine was arrested.

There was a heavy security presence around Wine's sprawling compound on Friday. The singer-turned-lawmaker said he was under siege and his life was in danger.

Police said that they had merely boosted their deployment in his neighbourhood for his security.

Wine said on Friday that he had video proof of voting fraud, and would share the videos as soon as internet connections were restored.

Electoral Commission Chairman Simon Byabakama said on Friday at a news conference that under Ugandan law, the burden of proof rested with Wine, whose real name is Robert Kyagulanyi.

Wine's claims have not been independently verified by Reuters. The United States and European Union did not deploy teams of observers for this election, though the African Union and East African Community did.

Neither the AU or EAC observer teams responded to requests for comment about possible irregularities.

On Wednesday, the government ordered an internet blackout until further notice, a day after banning all social media and messaging apps.

Wine and his supporters used Facebook to relay live coverage of his campaigns and news conferences after he said many media outlets had declined to host him.

The electoral commission has assured Ugandans that results were arriving at the national tallying centre, despite the internet blackout.