KAMPALA, Uganda—Ugandan police say they have restricted the movements of the capital's mayor, an opposition politician who is a fierce critic of the country's long-serving president.

Police spokesman Patrick Onyango said Thursday that Kampala Mayor Erias Lukwago was placed under what he called "temporary suspension" on Monday and cannot travel around the city.

The mayor is effectively under house arrest and is constantly monitored by police who are trying to quell a resurgence of protests against President Yoweri Museveni, who has been in power for 27 years.

Frederick Ssempebwa, a law professor at Uganda's Makerere University, said the country has become "an autocracy" despite the regularity of elections.

Police accuse Lukwago of running a "hate campaign" against the government and insist their tactics keep the city safe for all residents.