Emilian Kayima, a spokesman for Ugandan police, said the two men are likely to be charged with the offense of unlawful assembly for demonstrating without prior authorization of the police.
The men are members of Uganda's Democratic Party, one of several opposition groups.
The local Daily Monitor newspaper reported the two arrested were part of a larger group that carried placards including one saying "A Vote For Trump Is A Vote Against African Dictatorship!"
Ugandan President Yoweri Museveni has held power here for three decades.
Following disputed elections in February, Kizza Besigye, the main opposition figure, was charged with treason.
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