Iranian state television named a suspect in the attack that damaged uranium enrichment centrifuges at its Natanz nuclear site and claimed he fled the country "hours before" the attack.
The extent of the damage from the April 11 sabotage was unclear, but it happened as Iran tries to negotiate with world powers over allowing the US to re-enter the 2015 nuclear deal Tehran signed with those powers.
Iran also wants relief from economic sanctions.
State television identified the suspect as 43-year-old Reza Karimi. It showed a passport-style photograph of a man it identified as Mr Karimi and said he was born in the central city of Kashan.
The report also aired what appeared to be an Interpol red notice seeking his arrest.
The notice was not immediately accessible on Interpol's public database.
Interpol, based in Lyon, France, said it could not confirm that a red notice was issued for Mr Karimi.
The TV report said "necessary actions" were under way to return Mr Karimi to Iran through legal channels.
The report did not elaborate on how Mr Karimi would have got access to one of the most secure facilities in Iran.
However, it did for the first time show authorities acknowledging that an explosion struck the Natanz facility.
There was a “limited explosion of a small part of the electricity-feeding path to the centrifuges’ hall,” the TV report said. “The explosion happened because of the function of explosive materials and there was no cyber attack.”
Initial reports in Israeli media, which maintain close relations with military and intelligence services, blamed a cyber attack for the damage.
The Iranian state TV report also said there were images that corroborated the account of an explosion rather than cyber attack offered by security services, but it did not broadcast those pictures.
The report also showed centrifuges in a hall at Natanz, as well as what appeared to be barricade tape.
In one shot, a TV reporter interviewed an unnamed technician, who was shown from behind – likely to have been a safety measure as Iranian nuclear scientists have been murdered in suspected Israeli-orchestrated attacks in the past.
“The sound that you are hearing is the sound of operating machines that are fortunately undamaged,” he said, the high-pitched whine of the centrifuges heard in the background.
“Many of the centrifuge chains that faced defects are now under control. Part of the work that had been disrupted will be back on track with the round-the-clock efforts of my colleagues.”
Iran has begun enriching uranium up to 60 per cent purity in response to the attack – three times higher than before, although in small quantities.
In Vienna, negotiations over the deal continued on Saturday with another meeting of diplomats from Iran and the five powers that remain in the deal. Meetings of expert level working groups on sanctions and nuclear issues are set to continue until next week.
Iran’s negotiator told state TV that the talks had entered a new phase, adding that Tehran had proposed draft agreements that could be a basis for negotiation.
“We think that the talks have reached a stage where parties are able to begin to work on a joint draft,” Abbas Araghchi said. “It seems that a new understanding is taking shape, and now there is agreement over final goals.”
Enrique Mora, the European Union official who chaired the talks, tweeted that “progress has been made in a far from easy task. We need now more detailed work.”
The 2015 accord, which former President Donald Trump unilaterally withdrew the US from in 2018, prevented Iran from stockpiling enough highly-enriched uranium to be able to pursue a nuclear weapon if it chose in exchange for the lifting of economic sanctions.
Iran insists its nuclear programme is peaceful, although the West and the International Atomic Energy Authority said Tehran had an organised military nuclear programme up until the end of 2003.
An annual US intelligence report released on Tuesday continued with the longtime US assessment that Iran is not currently trying to build a nuclear bomb.
Iran previously had said it could use uranium enriched up to 60 per cent for nuclear-powered ships. However, Tehran has no such vessels in its navy.
The attack at Natanz was initially described as a power cut in its electrical grid – but later Iranian officials began calling it an attack.
One official referred to "several thousand centrifuges damaged and destroyed" in a state TV interview.
However, no other official has offered that figure and no images of the aftermath have been released.
