An Iranian-American journalist who once worked for a US government-funded broadcaster is believed to have been detained by Iran for months now, authorities said on Sunday, further raising the stakes as Tehran threatens to retaliate over an Israeli attack on the country.

The imprisonment of Reza Valizadeh, acknowledged by the US State Department, came as Iran on Sunday marked the 45th anniversary of the American Embassy takeover and hostage crisis. It also followed Iran’s Supreme Leader Ayatollah Ali Khamenei threatening both Israel and the US the day before with “a crushing response” as long-range B-52 bombers reached the Middle East in an attempt to deter Tehran.

Valizadeh had worked for Radio Farda, an outlet under Radio Free Europe/Radio Liberty that is overseen by the US Agency for Global Media. In February, he wrote on the social platform X that his family members had been detained in an effort to see him return to Iran.

In August, Valizadeh apparently posted two messages suggesting he had returned to Iran despite Radio Farda being viewed by Iran’s theocracy as a hostile outlet.

“I arrived in Tehran on March 6, 2024. Before that, I had unfinished negotiations with the [Revolutionary Guard’s] intelligence department,” the message read in part. “Eventually I came back to my country after 13 years without any security guarantee, even a verbal one.”

Valizadeh added the name of a man who he claimed belonged to Iran’s Intelligence Ministry. Journalists could not verify if the person worked for the ministry.