The State Department reissued a travel warning Monday that emphasized the risks facing U.S. citizens in Iran.

"Iranian authorities continue to unjustly detain and imprison U.S. citizens, particularly Iranian-Americans, including students, journalists, business travelers, and academics, on charges including espionage and posing a threat to national security," the warning reads. "U.S. citizens traveling to Iran should very carefully weigh the risks of travel and consider postponing their travel."

Iran "does not recognize dual citizenship," the warning says, and the Iranian government will treat dual citizens as Iranians "without regard to … personal wishes."

The statement also highlights the continuing threat that a range of religious and ethnic groups, "including Christians, Baha'i, Arabs, Kurds, Azeris, and others," face in the Islamic Republic.

Despite the warning, Iran remains a tourism destination for some. The New York Times offers two-week trips to Iran several times a year.

"Though Iran often rejects Western ways and is frequently under fire for its positions on human rights, its nuclear program and Israel, its role as a birthplace of civilization cannot be denied," the trip description says. "Welcome to the once-forbidden land of Iran."

The Nation is also offering a week-and-a-half long "educational excursion" to the Islamic Republic this December.

The State Department warning comes amidst controversy over a $400 million payment the Obama administration made to Iran and used as "leverage" in the return of three Americans held hostage there in January.

Since the payment, which was part of a larger $1.7 billion legal settlement for a decades-old arms deal, Iran has taken at least two more Americans hostage.

The State Department in June said that Iran "remains the foremost state sponsor of terrorism in 2015," due to its support for terrorist groups like Hezbollah and the Palestinian group Hamas.

The human rights situation has also not improved there, despite the election of Hassan Rouhani, a "moderate candidate," as president in 2013, according to Human Rights Watch.