Several TV channels showed a short clip in which Ukrainian soldiers call for silence ahead of the upcoming counteroffensive.
The hacker attack took place on Sunday, as confirmed by Oleg Kruchkov, an adviser to the governor of Crimea, which was annexed by Russia in 2014.
When does the Ukrainian counteroffensive start?
On Saturday, Ukrainian President Volodymyr Zelenskyy announced that the country is now ready to launch the counteroffensive, but that it will not announce when and where it will begin. And Ukraine has since continued to deny that the counteroffensive has started.
According to Russia, however, the counteroffensive is already underway. On the night of Monday, the Russian Defense Ministry claimed in a message on Telegram that Ukraine had launched the offensive on Sunday.
Russia says the counteroffensive started in five different locations at Donetsk and said "the enemy has failed to achieve its objectives."
According to the Russian Armed Forces, 250 Ukrainian soldiers have been killed and 16 tanks have been knocked out in the attack. Ukraine has not commented on the data.