Ugandan police fired tear gas on Monday to disperse opposition supporters as they arrested a top presidential challenger, Kizza Besigye, days ahead of presidential polls, reports said.

"The arrest followed chaotic scenes as Besigye campaigned in parts of Kampala," the state-run New Vision newspaper reported, adding that tear gas was fired. The Daily Monitor newspaper reported he was arrested after trying to hold a rally in the centre of the capital, which police blocked.

Besigye, a three-time failed presidential candidate, heads the Forum for Democratic Change (FDC) party. He has been repeatedly arrested in the past, and is commonly released without charge hours later.