Iranian forces have arrested an "agent" of an opposition television broadcaster, Iran International, while the individual was fleeing the Middle Eastern country, its semi-official Fars news agency said.
The action comes amid the biggest challenge to Iran's clerical rulers since the 1979 revolution, sparked by nationwide protests after the Sept 16 death of Mahsa Amini in the custody of morality police for not wearing "appropriate attire".
On Tuesday, Iran's intelligence minister, Esmail Khatib, called the London-based channel a "terrorist" organisation.
"Recently, the agent carried out numerous activities and actions in slandering the Islamic Republic, inviting youth to riot and creating terror among the people," the agency added, describing the arrested person.
Officials of the broadcaster were not immediately available for comment.
Iran believes Saudi Arabia is behind the opposition news outlet which has covered the protest movement extensively since it started.
On Wednesday, Khatib warned Riyadh there was no guarantee Tehran would continue to maintain "strategic patience" towards its regional rival.