BOSTON (AP) — Iran is responsible for emails meant to intimidate American voters and sow unrest in multiple states, U.S. officials said Wednesday night in calling out both Tehran and Russia for activities meant to interfere in the upcoming presidential election.

The announcement at a rare news conference just two weeks before the election underscored the concern within the U.S. government about efforts by foreign countries to spread false information meant to suppress voter turnout and undermine American confidence in the vote.

“These actions are desperate attempts by desperate adversaries,” said John Ratcliffe, the government's top intelligence official, who, along with FBI Director Chris Wray, insisted the U.S. would impose costs on any foreign countries that interfere in the 2020 U.S. election.

Both countries have also obtained voter registration information, though such data is considered easily accessible. Despite the Iranian and Russian actions, the officials said Americans can be confident that their vote will be counted.

While state-backed Russian hackers are known to have infiltrated U.S. election infrastructure in 2016, there is no evidence that Iran has ever done so. Cybersecurity experts consider it to be a second-rate actor in online espionage.

The news conference was held as Democratic voters in at least four battleground states, including Florida and Pennsylvania, have received threatening emails, falsely purporting to be from the far-right group Proud Boys, that warned “we will come after you” if the recipients didn't vote for President Donald Trump.

The voter-intimidation operation apparently used email addresses obtained from state voter registration lists, which include party affiliation and home addresses and can include email addresses and phone numbers. Those addresses were then used in an apparently widespread targeted spamming operation. The senders claimed they would know which candidate the recipient was voting for in the Nov. 3 election, for which early voting is ongoing.

Federal officials have long warned about the possibility of this type of operation, as such registration lists are not difficult to obtain.

“These emails are meant to intimidate and undermine American voters’ confidence in our elections,” Christopher Krebs, the top election security official at the Department of Homeland Security, tweeted Tuesday night after reports of the emails first surfaced.