Three Molotov cocktails were thrown at the premises of a police headquarters in Minsk, the Belarusian Interior Ministry said.
The incident took place at about 5 am.
A video was shared by the ministry, showing three bottles being thrown into the yard of a police headquarters, one of them hitting a police bus.
An investigation is underway to identify the malefactors, the ministry said.
The incident comes amid continuing unauthorised protests in Minsk as well as in other Belarusian towns, which started two months ago after the widely disputed results of the presidential elections in the republic, which saw Alexander Lukashenko retain his position.
According to the election committee, his major rival, Svetlana Tikhanovskaya, got only slightly more than 10% of the votes; her supporters insist that the results were rigged, citing exit polls, and that it was she who won the election.