Emergency services today were holding scheduled drills across the vast country involving various disaster scenarios such as deadly explosions and fires.
The scenario concocted by officials for Tyumen -- an industrial region of 3.6 million people about 1,700 kilometres east of Moscow -- involved a toxic emission of chlorine gas at a waterworks.
But things went horribly wrong when the press office of Tyumen's emergencies ministry issued a statement reporting an "accident that resulted in the death of three workers and 52 members of the public."
The news was instantly picked up by Russia's state-run RIA Novosti news agency and radio stations such as nationally-syndicated Moscow Echo.
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It took about five minutes for officials to realise their mistake and issue a corrected version of the statement explaining that this was all just a training exercise and no one was really hurt.
"It was a poorly worded statement," an official with the Tyumen emergencies service told AFP by telephone.
"We are looking into it -- we have been getting a lot of calls about it."
Yet the false information spread like wildfire across Russian social networks. Komsomolskaya Pravda popular daily wrote that its Tyumen office was inundated with calls.
"At about noon, our office was flooded with calls from panicked citizens who believed that something terrible had really happened in Tyumen."
Various hashtags involving Tyumen and emergencies ministry also skyrocketed into the most popular on Twitter social network in Russia.
"After such 'training exercises' involving a 'scenario' with 55 bodies, you really could end up with 55 deaths -- from heart attacks," Russia's popular opposition leader Alexei Navalny tweeted.