Almost 50 people died and some 250 protesters were injured in clashes with the radicals, according to the United Nations.
The clashes in Odessa became one of the deadliest events during the series of Maidan and anti-Maidan demonstrations in Ukraine that started in late 2013.
Moscow has repeatedly slammed Kiev's steps in the investigation of the deadly tragedy and urged the international community and human rights groups to probe the causes of the massacre.