I was reading the wikipedia page on Lev Chernyi (Russian anarchist) and it mentioned this incident:
On September 25, 1919, together with a number of leftist social revolutionaries, the Underground Anarchists bombed the headquarters of the Moscow Committee of the Communist Party during a plenary meeting. Twelve Communists were killed and fifty-five others were wounded, including eminent Bolshevik theorist and Pravda editor Nikolai Bukharin.[7] Chernyi was detained along with Fanya Baron on a counterfeiting charge.[8] In August 1921, the Moscow Izvestia published an official report announcing that ten "anarchist bandits", among them Chernyi, had been shot without hearing or trial. However, historian of anarchism Paul Avrich contends that Chernyi was executed in September of that year rather than August.[1] Although he was not personally involved in the bombing of the Communist Party headquarters, Chernyi was, because of his association with the Underground Anarchists, a likely candidate for a frameup. The Communists refused to turn over his body to his family for burial, and rumors persisted that he had in fact died of torture.
Does anybody know more about who the Underground Anarchists were or about the nature of this incident?
Berkman mentions it
http://dwardmac.pitzer.edu/Anarchist_archives/bright/berkman/iish/rusrev/russianrevandcp.html