KAMPALA, Uganda — A prominent opposition figure in Uganda has been detained after violent clashes Monday night that allegedly started when President Yoweri Museveni’s motorcade was pelted with stones, a military official said Tuesday.

Lawmaker Kyagulanyi Ssentamu was held overnight in the northwestern town of Arua, where he and other politicians, including Museveni, had been campaigning for a lawmaker, said Capt. Jimmy Omara, a spokesman for the Special Forces Command.

Ssentamu, a popular pop singer in his 30s who was elected to the National Assembly last year, has emerged as a powerful voice with his calls for young people to “stand up” and take over this East African country from what he calls the current government’s failed leadership. Many followers urge him to run in the next presidential election in 2021.

Ssentamu said on Twitter that his driver was shot dead by police “thinking they’ve shot at me.” He posted a photo of a bloodied man slumped in his car seat.

Police spokesman Emilian Kayima said an unidentified man had been killed as security forces tried to “calm down the situation” after Museveni’s convoy came under attack from opposition supporters throwing stones.

Lawmaker Allan Ssewanyana, a close ally, said he was concerned for his colleague Ssentamu after being unable to reach him by phone.

Some journalists, including two reporters for local broadcaster NTV, also were detained. In a statement, NTV said its reporters were “violently arrested by armed men in military fatigues while reporting live on air” before being taken to an unidentified place and “physically assaulted repeatedly.” They later were charged with inciting violence and malicious damage to property and released.