An analysis of thousands of automated tweets showed that the results of the snap elections in the United Kingdom last year may have had Russian intervention in favour of the Labour Party.

Prime Minister Theresa May had called for elections in June 2017 in a bid to strengthen support for her Conservative Party, but she only narrowly managed to retain power after Labour performed beyond expectations.

A research by The Sunday Times and academics at Swansea University showed that over 6,500 Russian Twitter accounts shared posts supporting Labour Party’s Jeremy Corbyn and attacking Theresa May in the run-up to the elections. Such posts were shared with millions of voters as tweets and retweets. Most of the accounts were internet robots with female British names, and 80% of them had been created just weeks before the elections, the research showed.

Corbyn, who had just about 25% approval ratings before the polls that May was widely expected to win, saw his support swell to 40% by the end of his election campaign, according to The Times. He has recently been criticised over his reluctance to strongly condemn Moscow for its alleged role in the nerve agent attack on a former Russian spy in England.

While there has been speculation over Russia’s meddling in the 2016 United States presidential elections, this is the first report that shows Moscow may have interfered in the UK as well. Around 90% of the tweets about Corbyn’s party praised and promoted him, while a similar proportion of posts about May’s party were hostile, The Times reported.

Researchers said the fake accounts were just the tip of the iceberg. They urged Twitter to investigate the true scale of Russian meddling in British politics.

“These new revelations are extremely concerning,” the UK’s Digital and Culture Minister Matt Hancock said. “It is absolutely unacceptable for any nation to attempt to interfere in the democratic elections of another country.”