Salehi, head of the Iran's Atomic Energy Organization, said authorities had been aware of the suspects' activities for some time. Salehi said the four suspects were arrested in one of the country's nuclear facilities, the official news agency IRNA reported.
"The people were identified at first, but were allowed to continue their activities for a while. Then they were captured at the right time and are now under interrogation. Several cases have been identified so far and four people have been arrested in the recent case," the news agency quoted him saying. "We are vigilant and are observing the situations to prevent any adverse incident."
Shortly after the release of the Iranian report Sunday, Israeli Prime Minister Binyamin Netanyahu said Israel does not oppose diplomatic negotiations with Iran, but Iran must not be allowed to continue enriching uranium.
"Iran claims that it wants this capability for nuclear energy for peaceful needs. Seventeen countries in the world produce nuclear energy for peaceful needs without one centrifuge or enriching uranium," Israeli Radio quoted Netanyahu saying.
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