An Iranian hacking group is actively scouting U.S. election-related websites and American media outlets as Election Day nears, with activity suggesting preparations for more "direct influence operations," according to a Microsoft blog published on Wednesday.

The hackers – dubbed Cotton Sandstorm by Microsoft and linked to Iran's Islamic Revolutionary Guard Corps – performed reconnaissance and limited probing of multiple "election-related websites" in several unnamed battleground states, the report said. In May, they also scanned an unidentified U.S. news outlet to understand its vulnerabilities.

U.S. Vice President Kamala Harris, the Democratic candidate, faces Republican rival Donald Trump in the Nov. 5 presidential election, which polls suggest is an extremely tight race.

"Cotton Sandstorm will increase its activity as the election nears given the group's operational tempo and history of election interference," researchers wrote. The development is particularly concerning because of the group's past efforts, they said.

A spokesperson for Iran's mission to the United Nations said that "such allegations are fundamentally unfounded, and wholly inadmissible."

"Iran neither has any motive nor intent to interfere in the U.S. election," the spokesperson said.

In 2020, Cotton Sandstorm launched a different cyber-enabled influence operation shortly before the last presidential election, according to U.S. officials. Posing as the right-wing "Proud Boys," the hackers sent thousands of emails to Florida residents, threatening them to "vote for Trump or else!"

The group also released a video on social media, purporting to come from activist hackers, where they showed them probing an election system. While that operation never affected individual voting systems, the goal was to cause chaos, confusion and doubt, senior U.S. officials said at the time.

Following the 2020 election, Cotton Sandstorm also ran a separate operation that encouraged violence against U.S. election officials who had denied claims of widespread voter fraud, Microsoft said.

The Office of the Director of National Intelligence, which is coordinating the U.S. federal effort to protect the election from foreign influence, referred Reuters to a past statement that said: "Foreign actors — particularly Russia, Iran, and China — remain intent on fanning divisive narratives to divide Americans and undermine Americans’ confidence in the U.S. democratic system."