Iranian protesters have rallied outside the Swiss Embassy in Tehran, which represents American interests, to condemn the detention in Washington of Press TV journalist and news presenter Marzieh Hashemi.

During the demonstration on Sunday, the participants demanded the immediate release of the American-born journalist, who has been imprisoned in the United States without charge for a week.

University students, media workers and activists were among the protesters, who were chanting slogans and holding posters reading “Free Marzieh Hashemi.”

🔴 LIVE: Iranians gather outside U.S. interest section of Swiss embassy to protest Press TV anchor arrest https://t.co/08nMGtF4y3 — Press TV (@PressTV) January 20, 2019

Meanwhile, a twitter storm has been organized for January 20 at 17:00 GMT as part of a social media campaign to increase pressure for her release.

Hashemi, who has been living in Iran for years, was detained by the FBI at the international airport in St. Louis, Missouri, on January 13 while making a family visit.

After days of silence, a federal US court order confirmed on Friday that she had been arrested on a “material witness” warrant and was not accused of any crime.

The court order also noted that Hashemi was expected to be released from a detention facility in Washington after testifying before “a grand jury investigating violations of US criminal law.”

So far, the journalist has made two court appearances.

In a message released on Saturday, Hashemi's friends and family said that she must be immediately freed.