Ukrainian forces have launched a “large-scale operation“ to retake the eastern town of Slovyansk, according to pro-Russian separatists in the rebel stronghold.
Gunfire is said to have been heard. Russian media reports quote an insurgent leader as saying that two helicopters have been shot down.
In Kyiv, an aide to Ukrainian Interior Minister Arsen Avakov said he could not comment.
“Until it’s over, no one will say anything,“ he said.