Russia's Investigative Committee announced Monday that it was launching a criminal case against the Ukrainian leadership for the genocide of the Russian-speaking population of eastern Ukraine.
In a statement published on its website, the Investigative Committee accused Ukraine of having ordered the "complete elimination" of Russian-speakers during the conflict.
The Ukrainian prosecutor-general, in turn, said it has opened a criminal investigation against officials of Russia's Investigative Committee, the body investigating the alleged "genocide" by Ukrainian officials.
Ukrainian forces and pro-Russian separatists have been fighting for five months in eastern Ukraine, leaving at least 3,000 people dead and causing hundreds of thousands to flee their homes.
Kyiv and Western countries accused Russia of supporting the rebels and sending troops and hardware, charges that Moscow denies.
A September 5 cease-fire has ended most hostilities.