At least 50 people have been arrested in Uganda's capital, Kampala, as politician and musician, Bobi Wine, was cleared by the electoral commission to run in next year's presidential election.
Chaos broke out after police fired tear gas at supporters who had escorted him.
He is among 11 candidates challenging President Yoweri Museveni, who has been in power since 1986.
The election will be held in February next year.
Bobi Wine, 38, has shaken up politics in Uganda since he was elected to parliament in 2017.
Since he expressed his presidential ambitions, police and the military have repeatedly dispersed his rallies, and beaten and detained his supporters.
Last year, he was charged with intending to "alarm, annoy or ridicule" the president. He was also charged with inciting violence after being accused of calling on his supporters to physically harm the president.
He has denied the allegations.
He told the BBC in 2019 that his popularity, especially among the youth, is based on "people.. not just following me. But are following an idea".
What happened in Kampala?
From early in the morning, armed police and the army deployed heavily along the route Bobi Wine used to get to the nomination centre.
Presidential aspirants are only allowed to take small delegations with them to register for the election, as a coronavirus prevention measure, the BBC's Patience Atuhaire reports from Kampala.
The politician was accompanied by supporters running alongside his car, while others adorned in the red colour of his People Power Movement followed the procession on motorcycles.
Police fired teargas to disperse the procession, clashes then ensued resulting in several people being injured including police officers.
What happened to Bobi Wine?
After Bobi Wine handed his papers as the presidential candidate for the National Unity Platform (NUP), he was forced into a police van and driven home.
But he refused to get out of the vehicle, insisting that he needed to make his way to the party headquarters for the manifesto launch.
Speaking to his supporters at home, Bobi Wine said that the police had pepper-sprayed him and his colleagues in the eyes.
Uganda's electoral body has banned public rallies, and candidates are expected to campaign through mainstream and social media.