Uganda's main opposition leader Kizza Besigye has been taken into police custody after vowing to lead a protest march against President Yoweri Museveni's election victory.

Mr Besigye was bundled into a police van when he tried to leave his home, where he had been under house arrest.

His wife Winnie Byanyima said it was like a "military barracks" outside their home, in a post on Twitter.

Mr Museveni won Thursday's poll by a landslide to extend his 30-year rule.

Mr Besigye said the result had been rigged, while foreign observers said the poll had been marred by fear and intimidation.

In a BBC interview, Mr Museveni rejected allegations of vote rigging, and accused Mr Besigye of planning to incite violence.

Responding to criticism from European Union observers that the electoral commission "lacked independence and transparency", Mr Museveni told the BBC's Zuhura Yunus that "those Europeans are not serious".

"Transparency is what we've been voting for," he added.

Mr Besigye had vowed to march to the headquarters of the Electoral Commission to ask for a copy of the official declaration of results.

Official results gave Mr Museveni nearly 61% of the votes, with Mr Besigye taking 35%.

It was the fourth time Mr Besigye, candidate for the opposition Forum for Democratic Change party, had lost to Mr Museveni.

The two men were once allies, with Mr Besigye serving as Mr Museveni's personal doctor when they were guerrilla fighters.

Mr Museveni seized power in 1986 and is credited with restoring stability to Uganda. However, critics say he has become increasingly authoritarian.