Ugandan opposition leader Bobi Wine has said he was "grabbed" by "goons" and put under house arrest on his return from South Africa.
The singer-turned-politician is the strongest challenger to President Yoweri Museveni, who has held office for almost 40 years.
The 41-year-old has been arrested numerous times and has faced several charges, including treason.
Police denied arresting Bobi Wine, saying he was merely "escorted" home.
"Disregard rumours of his arrest by propagandists," the police said in a statement.
Bobi Wine, a former pop star whose real name is Robert Kyagulanyi, made a failed bid for the presidency in 2021 in a tense election against President Museveni, 79.
The election campaign was marked by a crackdown on the opposition and at least 54 people were killed during anti-government demonstrations.
Bobi Wine arrived on Thursday, via the Rwandan capital, Kigali, following a series of international engagements.
His supporters had planned to welcome him at Entebbe International Airport and accompany him to his home about 50 km (30 miles) away in a huge march, but the police said this was illegal.
Bobi Wine said that as soon as he landed, even before he had gone through immigration, "goons grabbed me and dragged me, twisted my hands and bundled me into a waiting private car".
He later said from his home that he was under house arrest.
A video posted by his National Unity Platform (NUP) on X, formerly Twitter, showed the leader being led away after disembarking from a plane in Entebbe. One of his associates was heard on the video saying "Where are you taking him?"
"The cowardly regime has arrested our president upon arrival at Entebbe Airport. We set out to receive him today, but the panicky regime security could not even allow him into immigration," said Mathias Mpuuga, the NUP leader in parliament.
Police later fired tear gas to prevent a group of his supporters from reaching his home.
Bobi Wine's return was eagerly anticipated by members of his party, who view him as a symbol of change for young people in a country ruled for decades by one man.
Last month, police announced they were banning NUP rallies across the country because of public order issues.
Ugandan soldiers and other security forces had been deployed on roads leading to Entebbe airport since early on Thursday morning, as well as outside the NUP offices, and in Kampala's central business district.
Police spokesman Patrick Onyango said security agents had accompanied Bobi Wine to his residence in Magere, Kasangati.
Ugandan authorities have a long history of using so-called "preventative arrest" to detain opposition leaders, often holding them for several hours before returning them to their homes so as to stymie mass demonstrations.
