One of the protesters' signs featured the words “Hitler also had a high [approval] rating.”

A protest initially sanctioned by city officials took a sour turn on Saturday as activists produced a sign comparing President Vladimir Putin's popularity with that of Nazi leader Adolf Hitler, news site OVD-Info reported.

Three protesters were detained during the event. Identified as Valery Nadezhdin, Alex Trofimov and Yury Konstantinov of the pro-democracy Solidarity movement, the detained activists were among the handful of demonstrators that gathered near Proletarskaya metro station on Saturday to protest Russia's policy toward Ukraine.

Police officers reportedly told Nadezhdin, the protest's organizer, that the event had digressed from its stated goal of "expressing a position on the political and economic situation in the country and in the world," which had been approved by city authorities.

One of the signs protesters carried featured caricatures of Putin and Hitler and the words "Hitler also had a high [approval] rating," according to the OVD-Info, a site that focuses on arrests and detentions.

Liberal-leaning television channel Dozhd reported that two "aggressive" men had attacked the protesters, one of whom snatched the Russian and Ukrainian flags they were waving and threw them in the dirt. Police also allegedly asked protesters to conceal the Ukrainian flag, according to Dozhd.

All three activists were released later the same day, OVD-Info reported.

Earlier this month, another member of Solidarity, 79-year-old Vladimir Ionov, became the first person to be charged with repeated violations of Russia's law on unsanctioned protests. Ionov could face up to five years in prison.

3 Detained at Sanctioned Moscow Protest