Iran said yesterday it had foiled a "sabotage attack" which targeted a building belonging to the Atomic Energy Organisation of Iran, without causing damages or casualties, state television reported.
"The saboteurs failed to carry out their plan, and there were no casualties or damage," the station reported.
Meanwhile, Tasnim news agency said the building was near the city of Karaj, 50 kilometres west of the capital, Tehran.
Other media reports said the competent authorities are investigating the attempted attack, which was carried out by drone.
The attempted attack comes as Tehran and the world's major powers are engaged in talks in the Austrian capital, Vienna, to revive the 2015 nuclear agreement, from which the United States unilaterally withdrew three years ago.
Earlier on Sunday, Iran's state television reported that the country's sole nuclear power plant has undergone an unexplained temporary emergency shutdown.
An official from the state electric company Tavanir, Gholamali Rakhshanimehr, said the Bushehr plant shutdown began on Saturday and would last "three to four days".