May 1 is Spring and Labor Day across Russia, a national holiday. In Soviet times May 1 saw massive Communist Party rallies.
Moscow police reported that as of 12:30 p.m. Moscow time [08:30 GMT] around 25,000 people were taking part in events in downtown Moscow to mark the day, including demonstrations by the ruling United Russia party, the Communists and trade unions, the ultranationalist LDPR Party and the liberal Yabloko party.
No public order problems have been reported in Moscow, but police have detained 120 nationalists, anti-fascists and anarchists following demonstrations in St. Petersburg. Police seized a number of knives and rubber-bullets pistols.