Investigators also summoned the opposition leaders for questioning. They are to report to authorities on Tuesday, which would make it difficult for them to attend the scheduled demonstrations.
Those demonstrations will challenge the rule of President Vladimir Putin, who was recently elected to a third term as president following four years as prime minister. The decision to search protesters' homes on Monday evinces the administration's resolve to suppress a growing anti-Putin movement.
Tuesday is Russia Day, a national holiday. The protests -- there are several planned across the country -- will coincide with governmentally sanctioned gatherings and cultural events. The Interior Ministry has reported that 70,000 police officers and over 9,000 soldiers will be mobilized on Tuesday to tighten security in various cities.