A screenshot from the message posted on the Yaroslavl Region Prosecutor's Office website on Sunday morning.

On the eve of tomorrow's nationwide anti-corruption protests, scheduled to coincide with Russia Day, hackers broke into the Yaroslavl Region Prosecutor's Office's website and posted a joking message: “Stay at home. Or we'll put you in jail instead of Dimon.”

Dimon is a nickname for Prime Minister Dmitry Medvedev that became widely used after opposition leader Alexei Navalny's Anti-Corruption Foundation released a film entitled “He Is Not Dimon to You,” on March 2. The film details corruption among top Russian officials, including Medvedev, and served as the catalyst for protests held across Russia on March 26.

The hackers’ embedded the “He Is Not Dimon to You” YouTube video on the Prosecutor's Office website, adding: “The Prosecutor's Office calls on citizens not to yield to provocations and to stay away from the unsanctioned events!”

By 11:15am Moscow time, however, the post had been removed, but the cache remains.

Уже #Ихтамнет pic.twitter.com/kQXjsyXXZ4

— Догоняй! Е7Ы09 (@mix_voronezh) June 11, 2017

It's #Alreadygone

On Sunday morning, the Prosecutor's Office told the local publication YarNews, that it had been hacked:

К проверке будут привлечены специализированные подразделения правоохранительных органов области. По результатам проверки будут приняты меры прокурорского реагирования.

Special regional law enforcement units will audit the attack. Measures will be taken based on the Prosecutor's Office's response to the audit…

Monday's anti-corruption rallies, which are being organized by Navalny's foundation, will take place despite numerous attempts to discredit the protest movement. State-sponsored anti-Navalny videos have been uploaded on YouTube, and Navalny and his supporters have been the victims of a variety of attacks, including with the “brilliant green” antiseptic. Hundreds of demonstrators were detained at the March 26 anti-corruption rallies, the largest protests held in Russia since 2011-12.