A pop singer and prominent critic of Uganda's government was charged with unlawful possession of firearms and ammunition in a military court on Thursday for his alleged role in clashes in which the longtime president's motorcade was attacked by people throwing stones.

Lawmaker Kyagulanyi Ssentamu, whose stage name is Bobi Wine, was arrested in the northwestern town of Arua earlier this week. In a court session closed to reporters, he was remanded and will reappear on Aug. 23, the military said in a statement.

Ssentamu's wife insisted he doesn't know how to handle a weapon, and rights activists demanded his release. In a suburb of the capital, Kampala, small groups of his supporters took to the streets and burned tires in protest but police quickly dispersed them, national police spokesman Emilian Kayima said.

Three other lawmakers arrested alongside Ssentamu were charged earlier on Thursday with treason in a magistrates' court in the northern town of Gulu, where he was detained.

Many Ugandans expressed concern for Ssentamu's safety after Uganda's deputy prime minister told lawmakers he had been hospitalized in custody, without giving details.

The clashes broke out on Monday when Ssentamu and other politicians, including President Yoweri Museveni, were in Arua campaigning in a by-election to choose a lawmaker after the previous one was shot dead near Kampala in June.

Ssentamu's driver was shot dead in the clashes. The lawmaker later posted a picture of the dead man on Twitter, saying he had been killed by the police "thinking they've shot at me."

A group of lawmakers authorized by the parliamentary speaker to investigate the situation told reporters on Thursday that they had been unable to see the pop star.