(CNN) Twitter bots supporting the anti-immigration Sweden Democrats have almost doubled in the past month ahead of the Swedish election, according to a government agency.
A study of 571,719 tweets sent during March to August showed the number of accounts with automated behavior "increased significantly" in recent weeks, the Swedish defense research agency said.
The bots were 40% more likely to express support for the Sweden Democrats than genuine accounts, according to the agency. The ruling Social Democrats received the most criticism from the bots, but also came under fire from genuine accounts.
In a trend that echoes other recent elections around the world, both the Sweden Democrats and another far-right party, the Alternative for Sweden, received more support both from genuine and automated accounts than the other parties.
"The general picture that we paint is that these bots were spreading quite a lot of misinformation around the election," Ralph Schroeder, director of research at the Oxford Internet Institute and co-author of the study, told CNN. "Much of the conversation is about supporting certain parties, criticism of immigration and refugees, critique of the elites and of the media."
The Sweden Democrats party, with a far-right and anti-immigration agenda, has strong levels of support ahead of the September 9 vote, polls suggest, while the center-left Social Democrats party, which has dominated Sweden for decades, is polling below its historical levels.
During the period analyzed in the study, between 6% and 17% of the total content came from bots, the agency said. The variation is caused by Twitter closing down some of the automated accounts for spreading misinformation, according to the agency.
"Hopefully, this study contributes to a greater awareness of the possible effects of bots, so that more citizens make their decisions without being affected by them," said Johan Fernquist, a data-science researcher at the Swedish defense research agency and project leader for the study.
The study analyzed all the tweets from more than 46,000 accounts with hashtags linked to Swedish politics and elections, such as #svpol and # Val2018.
The agency did not say who might be behind the bots. "We can only say there are some actors behind them who are hiding their identity while engaging in high-degree political conversation," Schroeder said.
"Sweden still has a high regard for public service but this kind of misinformation paints a worrying picture for democracy," he added.
CNN has reached out to Twitter for comment and will update the article accordingly.