Iranian state media say Iran has arrested seven people linked to U.S.-funded Radio Farda and has accused some of working for U.S. spy agencies.
The official new agency IRNA says the seven are suspected of provoking protesters during the violent anti-government demonstration last December.
At least eight people died on Ashura, the day of ritual Shi'ite Muslim mourning, after clashes broke out between security forces and opposition supporters.
IRNA did not identify those arrested. Radio Farda is a Farsi-language broadcast service based in Prague, Czech Republic, and funded by the U.S. government.
The arrests come as Iran is beginning to mark the 31st anniversary of the 1979 Islamic revolution that toppled the U.S.-backed shah.
Opposition leaders Mir Hossein Mousavi and Mehdi Karroubi have urged their supporters to make their voices heard when Iranians march on February 11. Iran's government has threatened severe reprisals if the protests take place.
Some information for this report provided by AFP, AP and Reuters.