KAMPALA (Reuters) - Prominent Ugandan opposition lawmaker Robert Kyagulanyi arrived in the United States on Saturday to seek medical treatment for what he said was torture by authorities in his country.

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Kyagulanyi, a popular musician known by his stage name Bobi Wine, was elected last year and has amassed a large following among youth electrified by his scathing criticism of President Yoweri Museveni, sometimes delivered in his songs.

Protests had erupted in the Ugandan capital on Friday after police detained Kyagulanyi at the airport during a previous attempt to travel abroad for medical care.

In a tweet posted on Saturday evening, Kyagulanyi said: “Safely arrived in the US where I’ll be receiving specialized treatment following the brutal torture at the hands of SFC soldiers.” That referred to Uganda’s Special Forces Command.

“I will soon tell you what exactly happened to me since 13th August and what is next,” he said, referring to the day he was detained after being accused by authorities of throwing stones at a presidential convoy. He has pleaded not guilty to the charges.

Kyagulanyi posted in his tweet a picture of himself sitting in a wheelchair and holding crutches, posing in an airport next to his wife.

The lawmaker has said he was beaten up and tortured while in detention.

Ugandan authorities initially dismissed the allegations that Kyagulanyi was beaten up in detention as “rubbish” and “fake news.” But late on Friday a police spokesman said there would be an investigation into those allegations.

Kyagulanyi, who has emerged as a formidable threat to the president who has been in power for 32 years, was charged with treason over his alleged role in the stoning of Museveni’s convoy.

Museveni has won praise in the West for his opposition to militant Islam in the region, but many Ugandans regard the 73-year-old as out of touch with his people, nearly 80 percent of whom are under the age of 30.

He has been in power since 1986 and has repeatedly been accused by his opponents of rights abuses and the widespread use of security forces to suppress opposition to his rule. He denies charges that his government is involved in rights violations.