Three activists with the radical feminist Femen movement and a Russian photographer have spent the night in police custody after being detained on July 27.
The group claimed on July 28 that the four had been snatched off a street in Kyiv by unknown assailants in civilian clothes the previous afternoon.
Police say they were detained for disobeying police orders when the three activists were posing topless.
The activists -- Oleksandra Shevchenko, Yana Zhdanova, and Oksana Shachko -- now face charges of petty hooliganism, while the photographer is charged with disobeying a police officer.
They could face up to 15 days in jail.
Femen claims its activists have been beaten and harassed in the run-up to the visit to Ukraine by Russian President Vladimir Putin and other guests to mark the 1,025th anniversary of the Christianization of Kyivan Rus.
Based on reporting by AFP and Interfax