Opposition politician and music star Robert Kyagulanyi (aka Bobi Wine) was arrested by Ugandan police upon his arrival at the international airport in Kampala on Thursday.
Kyagulanyi had returned to Uganda from the United States, where he sought treatment after reportedly being tortured by the Ugandan security forces.
Authorities have however denied allegations of torture, whilst the police has stated that he was not arrested, but “peacefully escorted” home.
On the day of his return, officials closed roads and set up barricades in an apparent attempt to ban rallies welcoming Kyagulanyi home.
Several people who tried to welcome him at the airport were arrested.
Kyagulanyi has been previously charged with treason in August, alongside 32 fellow politicians, during a violent by-election.
He is seen as posing a credible threat to President Museveni, who has ruled Uganda since 1986.
Kyagulanyi “represents a youth voice that is social media-literate, hungry for economic development, and angry with the corruption and cronyism that has blighted the lives of generations,” BBC’s Africa editor, Fergal Keane said.
Supporters have started to wear red t-shirts and hats to express their solidarity with his “people power” movement, including supporters at Ugandan embassies in London, Nairobi and elsewhere.