Russian riot police ringed off the presidential administration building in Moscow on Saturday after a crowd gathered nearby following an opposition rally and hundreds more were seen walking toward the area chanting, Reuters witnesses said.

Police detained at least 120 people, according to the OVD-Info police-monitoring website, after more than 500 people were seen moving toward the area, many of them young and chanting: “Putin is a thief.”

Tens of thousands of Muscovites staged Russia‘s biggest political protest for years earlier on Saturday, rallying to demand free city-wide elections in spite of a government crackdown.