Uganda on Wednesday banned rallies to welcome a prominent opponent of President Yoweri Museveni home from the United States where he received treatment for injuries he said were sustained during torture by security forces.

The homecoming of Robert Kyagulanyi, a pop star and opposition lawmaker, could present a significant challenge to Museveni, who has ruled since 1986.

Kyagulanyi, 36, attracted a youth following through songs critical of Museveni and his prominence rose due to an incident in August in which his driver was shot dead and he was detained and charged with treason over what authorities said was the stoning of Museveni’s convoy.

He said in a tweet on Wednesday he was “headed home” and showed a picture of himself at an airport holding a walking stick.

Police said they had received information that supporters of Kyagulanyi, also known as Bobi Wine, planned to stage rallies and processions on his return but had not sought permission.

“As a result, they (the rallies) are unlawful and would disrupt normal business activities,” a police statement said.

Kyagulanyi has pleaded not guilty to treason charges.

He said he was beaten with an iron bar in detention in northern Uganda. The government denies that he was mistreated.

Kyagulanyi’s case sparked protests in Uganda’s capital Kampala and drew international condemnation from the government’s major backers including the EU and the U.S. The Pentagon has donated equipment and weapons to the unit of the Ugandan military accused by Kyagulanyi of torturing him.

In a statement on Tuesday five U.S. legislators said they were “gravely concerned” by the torture of the legislators and their supporters and described it as “unacceptable”. Five legislators in all were detained, two say they were badly beaten and all say they were mistreated.