Police immediately suspended Uganda's largest opposition party's nationwide mobilization campaign, led by Bobi Wine.
They claim the opposition is violating public order and defaming President Yoweri Museveni.
The National Unity Platform received formal approval for the operation, which began on September 2, a rare approval occurrence in a country where President Yoweri Museveni has tightly controlled opposition groups since 1986.
Despite the declaration, Wine told AFP that mobilization activities would continue around the country, with the most recent occurring on Wednesday in Arua, northwest.
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"We are continuing with our mobilisation irrespective what Museveni using police can dismally do to stop our popularity".
According to the police, "there have been breaches... causing public disorder, unnecessary traffic jams, loss of business, and malicious damage to property in all areas where the NUP mobilisation activities have been carried out."
They cited road accidents and one death in the western town of Hoima, as well as a meeting in central Uganda that incited "violence, sectarianism, illegitimate calls for the removal of an elected government, and the issuance of defamatory statements against the president's person."
"The activities of the National Unity Platform are immediately suspended."
Wine, real name Robert Kyagulanyi, a former singer, claimed he expected the ban.
"We are continuing with our mobilisation regardless of what Museveni can dismally do with police to stop our popularity," declared the president's main contender in his next re-election in 2021.
Wine has been jailed several times, and 54 people were killed when security forces broke up a pre-election campaign meeting.