A lead car in Ugandan President Yoweri Museveni's motorcade has been vandalised in chaos and gun fire that rocked a by-election campaign in the town of Arua, some 440 kilometres north-west of the capital Kampala, the Daily Monitor reported on Tuesday.

Museveni’s motorcade was attacked on Monday night by opposition supporters at Prisons Cell as he left the Boma grounds where he had held his last rally campaigning for Nusura Tiperu, a candidate for the ruling National Resistance Party in Wednesday’s by-election.

The violence also saw the driver of prominent opposition activist and Kyadondo East MP Robert Kyagulanyi, alias Bobi Wine, shot dead during clashes that conjured up memories of how the seat fell vacant - the assassination of area MP Ibrahim Abiriga in June.

The whereabouts of Wine, seven of his aides and a number of journalists remain unknown.

The bloody confrontations began when rival candidates and their supporters marched to their respective offices after campaign rallies ahead of the by-election.

Supporters of MP Kassiano Wadri Kassiano, an independent but opposition-leaning candidate, were marching ahead of those of Tiperu.

Wine was in Arua to support Kassiano while Museveni was working to secure votes for Tiperu. The two leaders were however not part of the marches.

Kassiano’s group came under fire from Ugandan security forces, forcing supporters to scatter. His supporters then retaliated by throwing stones at the military and government supporters.