Iranian media say some 15 Iranian and foreign nationals have been arrested for alleged spying for Israel, attempted assassination, and sabotage.
The Intelligence Ministry is quoted as saying the suspects belong to an Israeli-linked "assassination" network.
It claimed Iranian intelligence uncovered a spy base of Israel's intelligence agency in a neighboring country.
It said the group also used Israeli diplomatic missions in Western countries to prepare plans.
The Iranian ministry said the group's mission was to "identify and assassinate one of our nation's experts and to bomb some of the nation's installations."
It did not identify the alleged targets.
At least four Iranian scientists thought to have been nuclear experts have been killed in the past two years.
Iran from time to time announces the arrest of suspected spies working for Israel or the United States.
Based on reporting by AFP and AP