"The Iranian regime, following the 12-day war with Israel, is in the midst of unprecedented paranoia and a crackdown on spies and regime opponents," the State Department said in a post on its Persian X account USA Beh Farsi.
"Anyone considering travel to Iran should reconsider their decision. We repeat: US citizens should not travel to Iran!" the post reads.
Iran recently arrested two American Jewish citizens on suspicion of spying for Israel in the aftermath of the recent 12-day war, Israel's Channel 11 reported.
One of the two detainees, identified by HRANA as 70-year-old Yehuda Hekmati, remains in detention.
Hekmati, a jeweler with ties to New York, allegedly drew the attention of the Islamic Republic due to a trip he made to Israel seven years ago.
The second detainee, an Iranian-American resident of Los Angeles, has been released on bail.
US State Department spokesperson Tammy Bruce declined to comment on the case Tuesday, saying only that she hopes she would be able to speak about it soon.
The State Department has repeatedly warned that Americans, including dual nationals, risk wrongful detention in Iran.
The department's website says: "Americans, including Iranian-Americans and other dual nationals, have been wrongfully detained, taken hostage by the Iranian government for months, and years."
Israel’s Channel 11 quoted a source involved in the American detainees’ case as saying, “These two Americans were in the wrong place at the wrong time.”