Besigye had been meeting a number of senior opposition figures in an upmarket suburb of the capital, Kampala, ahead of a rally to demonstrate against corruption and economic hardships.
Armed police intercepted the group on the highway as they headed towards the city centre. A protracted standoff ended when the police fired a single teargas cannister before bundling the politicians into vans. The protest failed to go ahead.
“We’re holding Besigye and others as a preventive measure because there was a likelihood of a breach of peace and chaos,” deputy police spokeswoman Judith Nabakooba told reporters outside the city police station.
“We’ll hold until we’re sure there is no more threat.”
Besigye, who served as Museveni’s doctor during the bush war that propelled him to power and later as a minister in his government before the pair fell out, told Reuters last week he would quit as head of his party to devote more time to planning protests.
Veteran leader Yoweri Museveni cracked down hard on a wave of protests against surging prices last year.
Besigye was arrested several times last year during violent clashes between the security forces and his supporters. In one of the protests, he was pepper-sprayed in the eyes and badly manhandled, and had to go to hospital in neighbouring Kenya.
The opposition-led Activists 4 Change group, which spearheaded those protests with Besigye, accused the government this week of “failed economic policies” that the group said had allowed the cost of living to soar.
Political analysts said the opposition was seeking to capitalise on the increasingly high cost of living and popular frustration at a number of corruption scandals, and to fan discontent.
“What’s not in doubt is that Museveni will still be president at the end of this year, albeit his power grip weakened to an extent,” columnist Nicholas Sengoba said.
“What the opposition is trying to do is erode a hard rock, chip by chip.”