Ukip have told Vladimir Putin to 'bot out' of the Stoke by-election
With the vote on a knife edge, the anonymous social media users have turned against Mr Nuttall with a huge number of negative messages and photos.
The accounts had been posting Russian propaganda until this week when they all promptly switched their focus to taking down the Ukip challenger.
Alex King, an independent researcher who uncovered the operation, said the campaign was coordinated using accounts unlikely to be linked to actual people.
With Russia already accused of interfering with the US election last year and the 2015 UK general elections, concerns are growing this is another example of Vladimir Putin attempting to affect another vote.
The Tweets instruct followers “don’t vote Nuttall” with many accompanied by the logo "Corbyn news" – although there is no evidence whatsoever the accounts are linked to the Labour Party.
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One of the anti-Ukip messages shared by the Russian bots
One message, accompanied by a photo of Mr Nuttall, asked: “Can this man be trusted?”
It included the accusation Mr Nuttall “lied” about losing friends in the Hillsborough disaster.
Another posted a photo of the Ukip candidate and the claim he would try to privatise the NHS. It warned: “Don’t by fooled”.
The Stoke by-election is set to go down to the wire
Bot out, Putin!
A spokesman for Ukip dismissed the seriousness of the allegation but did acknowledge the attack.
He said: “I don’t think people take a blind bit of notice. I don’t think the good people of Stoke are now avidly watching Russian automated Twitter bots. Bot out Putin!
“We are not Trump, we are not Clinton. The idea that Putin gives a flying rat’s a*** about Paul Nuttall winning in Stoke – I just don’t see it.”
One of the hundreds of anti-Nuttall posts shared by Russian accounts on Twitter
The by-election is set to come down to the wire with a poll this week predicting a dead heat between Labour and Ukip.
The Stoke Sentinel newspaper's survey revealed 26 per cent of voters would chose Labour and 25.8 per cent would chose Ukip.
Around 11 per cent would vote Conservative while 30.2 per cent would vote for one of a handful of other candidates from the BNP, Monster Raving Loony Party, the Christian Peoples Party and two independents.