KAMPALA (Reuters) - Ugandan police detained two lawmakers, one of whom is also a pop star, at the country’s sole international airport, where supporters say they were trying to seek treatment abroad for injuries suffered while being tortured by the security forces.

Allegations that Robert Kyagulanyi and Francis Zaake were tortured have triggered widespread protests in the capital Kampala and other parts of the country.

The two were among a group of five lawmakers that were detained on August 13 in Uganda’s northwestern town of Arua, accused of throwing stones at a presidential convoy during the campaign for a vacant seat in parliament. Kyagulyani is a pop star, known by his stage moniker Bobi Wine.

President Yoweri Museveni, in power since 1986, has repeatedly been accused by his opponents of rights abuses and widespread use of security personnel to suppress opposition to his rule. He denies that his government carries out abuse.

“The Uganda Police halted the departure of the Hon. Robert Kyagulanyi Ssentamu at Entebbe International Airport,” police tweeted late on Thursday. “Given the fact that he is on bail, the police is concerned and await for guidance from the relevant government department.”

In a separate statement on Thursday police said they had also found Zaake at Entebbe early on Thursday, “trying to flee the country and accordingly apprehended him.”

Kyagulanyi in particular has emerged as a formidable threat to Museveni’s 32-year rule, winning popular support through his music and strong criticism of the government.

In the days after the lawmakers were detained, allied politicians and relatives said the two were tortured and both needed to be taken outside the country for specialized medical care.

Kyagulanyi, who has been charged with treason alongside several others for his role in the stoning incident, used crutches in court appearances and was transported in an ambulance at times. His supporters say he was beaten with a metal bar while in detention.

Zaake has not been charged but has been at a hospital in the capital Kampala, with images of him posted on social media showing him lying on a bed, eyes closed, with multiple bruises on his hand and other body areas.

Police said he had been taken to the country’s national referral hospital in Kampala where he would be treated under custody. He would be charged “at an appropriate time” with offences from the stoning of the presidential convoy.