The Iranian Foreign Ministry denounced "the move by the USA, which detained Marziyeh Hashemi illegally and inhumanely", adding that "the US' actions with regard to her are a direct violation of human rights".
Zarif called the detention of one of its journalists in the United States a "political action" that tramples on freedom of speech and demanded her immediate release.
Upon arrival at St. Louis Lambert International Airport she was detained and transferred from Missouri to Washington DC, where she is now being held in an Federal Bureau of Investigation detention facility. He has said she's been jailed as a material witness, though it's unclear for which case.
The FBI, the Department of Justice and the Metropolitan Police Department in St. Louis all declined NPR's requests for information.
Press TV quoted Hashemi's daughter as saying the anchor had been given "a hijab (Muslim head covering) and food to get by" after it had earlier said prison officials had taken a photograph of her without her hijab and had not provided halal food.
Material witness warrants are rare. Only two such warrants were issued past year and both are still under seal, The Washington Post said in a report on Friday.
Hossein Hashemi, son of Marizeh Hashemi leaves federal court in Washington, on Friday.
United States District Court for the District of Columbia announced on January 18 that Hashemi is being held in detention in the U.S.as a material witness and has not been accused of any crimes. He said that neither his mother nor any of his family had testified and that "we don't anticipate her getting out today".
No official charges have been pressed against the Iranian anchorwoman. "We don't think any of that should lead to her arrest".
Hasemi told the Associated Press that he and his siblings had been subpoenaed to appear before a grand jury.
Hashemi's attorney, Preston Burton, said, "Marzieh Hashemi's perseverance has been remarkable in the midst of hard circumstances, and it is my privilege to represent her".
Hashemi worked for the Press TV network's English-language service.
"We want more clear answers", Hossein Hashemi said in a separate interview with Press TV.
Federal law allows judges to order witnesses to be arrested and detained if the government can prove their testimony has extraordinary value for a criminal case and that they would be a flight risk and unlikely to respond to a subpoena.
Howell's order said Hashemi had made two court appearances before a judge while represented by counsel.
The Associated Press said United States government officials expected her to be released immediately after her testimony before a grand jury, but Hashemi's elder son, Hossein, was pessimistic about prospects for her immediate release, saying it was not clear yet how long his mother's testimony would last.