Inspectors from the United Nations nuclear watchdog began their visit to a heavy water production plant that Iran agreed to open for inspection last month, Iranian state TV reported Sunday.
The report quotes Behrouz Kamalvandi, who is spokesman of Iran's nuclear department, as saying the two inspectors are at Arak heavy water production plant, some 250 kilometers (150 miles) southwest of Tehran.
Inspectors from the International Atomic Energy Agency, the IAEA, had visited the site twice over the past years.
Iran last month agreed to allow expanded UN monitoring at the country's nuclear sites, including the Arak site where plans for commissioning a plutonium reactor have been suspended under a separate interim deal reached with world powers.
The U.S. and its allies fear that Iran may finally be trying to develop a nuclear weapon, a charge Tehran denies.
Iranian President Hassan Rohani, meanwhile, said in Iran on Sunday that the last month's nuclear deal with world powers has already had a positive impact on the country's economy.
Rohani spoke Sunday while presenting next year's budget to parliament. He told an open session of parliament that, after the "success" of the talks, investors were gravitating to businesses and the stock exchange. State TV broadcast his speech.
"Economic activities have been shifted to the stock exchange from gold, hard currency and real estate," said Rohani.