The protection of Rafael Grossi is confirmed by the IAEA, headquartered in Vienna, the day after talks between Iran and the trio United Kingdom, France, and Germany were concluded in Geneva.
The talks concern Iran's nuclear energy program, and the three countries are threatening to reintroduce UN sanctions against Iran if an agreement on, among other things, inspections is not reached before the turn of the month.
Inspectors from the IAEA have returned to Iran to, among other things, monitor fuel transports to the country's nuclear power plant in Bushehr.
The presence of the inspectors at the nuclear power plant was confirmed by Grossi on Wednesday evening.
Iran suspended cooperation with the IAEA's inspectors in connection with the twelve-day war between Israel and Iran in June, when Israel's ally the US bombed nuclear facilities in Iran.
Details about the threat against the IAEA chief are not disclosed, but he is protected by the Austrian police's special unit Cobra.
