According to Iranian media reports, Tehran has arrested an unknown number of people it alleges were part of a plot to assassinate Iranian nuclear scientists.
On July 22, Iran's Fars and Mehr news agencies cited Intelligence Minister Heydar Moslehi as saying Tehran had interrupted two networks targeting Iranian scientists both inside and outside the country.
Moslehi did not provide any further details.
At least four nuclear scientists have been killed since 2010.
Fereydoun Abbasi Davani, now head of Iran's Atomic Energy Organization, was wounded in an attack in November 2010.
Iran is deadlocked with much of the international community over its nuclear program, which the United States and others believe is aimed at developing nuclear weapons.
Tehran says the program is exclusively peaceful.
Based on reporting by Reuters, Fars, and Mehr