Iran is behind attempts to hack into Republican and Democratic presidential campaigns and has already succeeded in compromising Donald Trump’s campaign, intelligence officials said in a statement issued Monday.

The joint statement from the Office of the Director of National Intelligence (ODNI), the Federal Bureau of Investigation (FBI), and the Cybersecurity and Infrastructure Security Agency (CISA) says:

We have observed increasingly aggressive Iranian activity during this election cycle, specifically involving influence operations targeting the American public and cyber operations targeting presidential campaigns.

This includes the recently reported activities to compromise former President Trump’s campaign, which the [Intelligence Community (IC)] attributes to Iran. The IC is confident that the Iranians have through social engineering and other efforts sought access to individuals with direct access to the presidential campaigns of both political parties. Such activity, including thefts and disclosures, are intended to influence the U.S. election process. It is important to note that this approach is not new. Iran and Russia have employed these tactics not only in the United States during this and prior federal election cycles but also in other countries around the world.

Protecting the integrity of our elections from foreign influence or interference is our priority. As the lead for threat response, the FBI has been tracking this activity, has been in contact with the victims, and will continue to investigate and gather information in order to pursue and disrupt the threat actors responsible.

In a statement, Iran’s Mission to the United Nations called the allegations “unsubstantiated and devoid of any standing.”

Last week, with Donald Trump already publicly pointing fingers at Iran, The New York Times reported that Trump adviser Roger Stone said he was contacted by Microsoft “a few months ago” about hackers that managed to get into his Hotmail account. He also said the FBI had informed him about unauthorized access to his Gmail that they believed had been used to get access to communications of other people in the Trump operation.

“The Islamic Republic of Iran harbors neither the intention nor the motive to interfere with the U.S. presidential election. Should the U.S. government genuinely believe in the validity of its claims, it should furnish us with the pertinent evidence—if any—to which we will respond accordingly,” the Permanent Mission of the Islamic Republic of Iran to the United Nations said in a statement emailed to The Verge.