Federal officials are warning that the threat environment across the United States has intensified after President Donald Trump approved a strategic airstrike in Iran, prompting major cities to ramp up security around religious and high-profile locations.

FBI and Department of Homeland Security leaders convened emergency calls on Sunday with governors and hundreds of law enforcement officials nationwide in response to Trump’s military operation targeting Iran’s nuclear facilities. While officials said there is currently no credible threat to the U.S. homeland, the federal government is urging heightened vigilance.