Kizza Besigye (pictured above, center) was arrested for the third time this week on Friday, a day after largely peaceful presidential polls were held in the country.

"Kizza Besigye has been arrested from our HQ and taken to [an] unknown location," Besigye's Forum for Democratic Change (FDC) party said in a message on Twitter.

Police fired tear gas, water cannons and stun grenades to disperse the leader's supporters outside FDC headquarters, Reuters news agency reported. Besigye and his supporters were then loaded on to the back of a police van and taken away.

The United States condemned Besigye's arrest. State Department spokesman John Kirby said the incident called into question Uganda's commitment to a transparent election free from intimidation.

Museveni leads in preliminary results

"Some reasonable measures have been applied to rein in FDC supporters who wanted to disturb the peace and the ongoing exercise," senior police officer Felix Andrew Kaweesi told the AFP news agency.

"Besigye knows very well that the mandate to declare electoral results lies with the electoral commission," he added, referring to Besigye's purported plan to publish poll results.

Preliminary results revealed Besigye had won 33 percent votes and was second after Museveni. The president was leading in Thursday's elections and had won more than 60 percent of the vote with ballots counted from 36.5 percent of voting stations, according to the electoral commission.

However, Besigye's party was running its own tally and discovered that the election commission's results were not accurate, Besigye aide Ingrid Turinawe told The Associated Press. She said the commission was announcing results according to polling stations and not according to districts, as was expected.

Besigye is the former physician of President Yoweri Museveni, who has been Uganda's president for the last 29 years. Besigye has lost three elections to Museveni, who is considered an ally of the West against threats from Islamist militants.

mg/sms (AFP, Reuters, AP)