A website called Savannah Time describes itself as “your trusted source for conservative news and perspectives in the vibrant city of Savannah.” Another site, NioThinker, wants to be “your go-to destination for insightful, progressive news.” The online outlet Westland Sun appears to cater to Muslims in suburban Detroit.

None are what they appear to be. Instead, they are part of what American officials and tech company analysts say is an intensifying campaign by Iran to sway this year’s American presidential election.

Iran has long carried out clandestine information operations against its adversaries, especially Israel, Saudi Arabia and the United States, but until now most of its activities were conducted under the shadow of similar campaigns by Russia and China. Its latest propaganda and disinformation efforts have grown more brazen, more varied and more ambitious, according to the U.S. government, company officials and Iran experts.

Iran’s efforts appear intended to undermine former President Donald J. Trump’s campaign to return to the White House, according to the officials and companies, but they have also targeted President Biden and Vice President Kamala Harris, suggesting a wider goal of sowing internal discord and discrediting the democratic system in the United States more broadly in the eyes of the world.

“Iran is becoming increasingly aggressive in their foreign influence efforts, seeking to stoke discord and undermine confidence in our democratic institutions,” Avril Haines, the director of national intelligence, warned recently.

Ms. Haines warned Americans to be wary “as they engage online with accounts and actors they do not personally know.”