Russian President Vladimir Putin says at least six people have been killed and many more injured in what he calls a "terrorist attack" on a building housing students in the occupied city of Starobilsk.
In front of television cameras, Putin said he had asked the military to prepare a retaliatory attack.
But the Kremlin's claims are denied by Ukraine's military leadership, which states that Ukrainian forces did not attack civilian infrastructure but attacked the headquarters of a Russian military unit.
"Manipulative information is being actively spread by Russian media," the Ukrainian General Staff wrote in a statement.
