Police departments from both New York and Los Angeles said they have increased security after threats from Iran.
Iran has promised a retaliatory attack after a U.S. airstrike killed a top Iranian general.
New York City Mayor Bill de Blasio said on Thursday that he has spoken with top officials from the NYPD about protecting key areas of the city.
"We will have to be vigilant against this threat for a long time to come," de Blasio said in his tweet.
The LAPD issued a similar statement, saying that it is monitoring events in Iran.
The LAPD said that there is currently no known, credible threat to the city.
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