The names of programmes on the schedule page were replaced to read: “The blood of thousands of Ukrainians and hundreds of their murdered children is on your hands.
“TV and the authorities are lying. No to war.”
The hack affected viewers of channels transmitted by MTS mobile operator, NTV Plus, Rostelecom and Wink. Three of the providers are owned by the Russian government while MTS is owned by billionaire Vladimir Yevtushenkov.
MTS said: “A cyberattack was carried out on Russian TV broadcasting channels, because of which subscribers could have extremist inscriptions in the broadcast grid.
“Now our IT specialists are promptly eliminating the consequences of hack so that subscribers can receive services and watch TV programs and movies as quickly as possible.”
Elsewhere in the Russian media, employees of formerly independent news site Lenta.ru changed the text of published articles on Monday to criticise Mr Putin and the war in Ukraine.
More than 10 articles appeared on the site with headlines including: “Putin unleashed one of the bloodiest wars of the 21st century”, “Vladimir Putin turned into a pathetic dictator and paranoid”, “Zelensky turned out to be cooler than Putin” and “Record spending on the army did not help Russia defeat Ukraine.”
Lenta did not comment but independent Russian news outlet Mediazone printed a statement from Lenta employees Yegor Polyakov and Alexandra Miroshnikova taking credit for the articles.
The pair said they were acting on conscience and believed they would no longer be able to work at Lenta.
Russia has been hit with several major media hacks since invading Ukraine as activists try to reveal the facts of the war to a sheltered Russian public.
Hacker group Anonymous targeted Russian state TV and streaming services in March, broadcasting footage from the invasion in place of the ordinary content.
Anonymous also claimed to have hacked printers across Russia to spread anti-propaganda messages.
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