WASHINGTON (AP) —  U.S. officials have accused Iran of being behind a flurry of threatening but fake emails sent to Democratic voters in Florida and other battleground states in a late-stage effort to sway public opinion and interfere in the presidential election.

Addressed as if from the far-right, pro-Trump Proud Boys group, the fake emails appeared aimed at intimidating voters. John Ratcliffe, the government’s national intelligence director, said the intent was to hurt President Donald Trump in the contest against Democrat Joe Biden, though he did not elaborate on how.

One possibility is the messages may have been intended to align Trump in the minds of voters with the Proud Boys after he was criticized for failing to unequivocally denounce the group during the first presidential debate. Google said in a statement that its spam filters stopped 90% of the roughly 25,000 emails sent to Gmail users.

Officials did not lay out specific evidence for how they came to pinpoint Iran, but the activities attributed to Tehran would mark a significant escalation for a country some cybersecurity experts regard as a second-rate player in online espionage. The announcement was made late Wednesday at a hastily called news conference 13 days before the election.

The allegations underscored the U.S. government’s concern about efforts by foreign countries to influence the election by spreading false information meant to suppress voter turnout and undermine American confidence in the vote. Such direct attempts to sway public opinion are more commonly associated with Moscow, which conducted a covert social media campaign in 2016 aimed at sowing discord and is again interfering this year, but the idea that Iran could be responsible suggested that those tactics have been adopted by other nations, too.

U.S. intelligence officials have repeatedly stated that they consider Russia the primary threat to U.S. election security, and Ratcliffe said Russia had also obtained voter data for potential mischief.