Several journalists, musician, and politicians also in custody.
Eddie Yamwa, the elder brother to Ugandan pop star-turned-lawmaker Robert Kyagulanyi, known as Bobi Wine, has been arrested at the Entebbe International Airport where he had gone to receive the Kyadondo East MP.
Mr Kyagulanyi is returning from a nearly three-week stay in the US where he was receiving specialised treatment after alleged torture by security forces.
Police and soldiers have barricaded roads around the airport ahead of the arrival of the President Yoweri Museveni critic on Thursday.
Several journalists headed to the airport, south of the capital Kampala, have been arrested while others have been blocked. Those arrested include NTV's Joel Ssenyonyi, Eve Muganga of Daily Monitor, Kingdom TV’s Siraje Kiberu and Radio Sapiensia's Charles Katabalwa.
Police have also seized musician Nubian Li, producer Dan Magic, ex-Makerere student leader Roy Semboga and opposition Democratic Party's Alex Mufumbira.
Meanwhile, Kampala mayor Mr Erias Lukwago has been placed under preventive arrest with police spokesman Emilian Kayima saying he would release a statement later.