There was no reason, he argued in a debate article for the Dagens Nyheter newspaper, to expect Sweden's poll not to be affected by the hacked emails, fake documents and social media spin had which plagued last year's US election campaign.
"There is nothing to suggest that that the future Swedish election is going to be free of this," he wrote. "On the contrary, we are already seeing clear signs of efforts to influence our security politics."
There were already clear signs, he said, of attempts to influence campaigns in France and Germany this year.
"This is an attempt from one country to affect another country's leadership, population or specific target group to push its own interest."
Russia, he added, was being "openly singled out".
In his article, Löfven announced that Sweden's security service Säpo planned to work with political parties to help them protect themselves from data intrusions.
Wikileaks last July published nearly 20,000 emails hacked from the servers of the Democratic National Committee.
In December the US's CIA foreign intelligence agency linked the intrusion to Russian attempts to sway the election.
Löfven said that the Swedish Civil Contingencies Agency (MSB) planned to gather together the Swedish media to inform them on how to ward off hacking attacks and other attempts to influence them.
Finally, he said that he had invited in the leadership of Sweden's political parties for a briefing from Säpo ahead of the poll.
"This is an issue which is above party politics and positions," he stressed. "It affects the foundations of our society," he wrote.
Löfven said attempts to influence the US, German and French campaigns had included the speading of fake documents by fictional people in social media, as well as more open displays of strength, smears and threats.
Löfven said that the new intitiatives built on work already done.
The Swedish Armed Forces was already strengthening the country's cyber defence, and was now able to carry out "active operations in the cyber environment", he said.
The National Defence Radio Establishment (FRA), which is responsible for signals intelligence, had installed special detection and warning systems to guard against foreign powers hacking into sensitive agencies.
The Swedish Agency for Public Management was coordinating Swedish public agencies which could carry out "psychological defence", and the Swedish Civil Contingencies Agency (MSB) had joined a Nato group coordinating eleven countries working against disinformation campaigns.