Iran has described an incident at its main uranium enrichment facility on Sunday as “nuclear terrorism” by countries seeking to spoil renewed efforts to save the nuclear deal it signed with world powers.

The head of Iran Atomic Energy Agency said a blackout at the underground Natanz site, the country’s main enrichment facility, was caused by those “who intend to prevent our nuclear industry’s development”.

“To thwart the goals of those who engineered this terrorist act, the Islamic Republic of Iran will continue to seriously develop nuclear technology on the one hand and expand its efforts to lift the unjust sanctions on the other hand,” Ali Akbar Salehi was quoted as saying to local media.

He added: “While condemning this vicious move, the Islamic Republic of Iran calls on the international community and the International Atomic Energy Agency to deal with this nuclear terrorism.”

He did not mention any country by name and gave no details of the damage caused, or whether it was a cyber attack. Israel and Iran are widely understood to have in the past targeted each other using cyber attacks.

The development comes at an important time for the Iran nuclear agreement, with the biggest effort under way to rescue the landmark deal since Donald Trump abandoned it almost three years ago.

Negotiations in Vienna last week were an attempt to bring the accord “back to life” after US President Joe Biden said Washington was prepared to rejoin if Tehran came back into compliance.

No direct talks between officials from Washington and Tehran are believed to have taken place but the presence of both countries at the same venue was seen as an important step.

But progress is likely to be slow, reflecting the internal pressures faced by both sides. Abbas Araghchi, Iran’s deputy foreign minister, said last week that “step-by-step” commitments in any new deal was not an option and that all sanctions imposed under the Trump administration must be lifted in one single step.

“We are still far from a concrete conclusion but I can say we are progressing well,” he said of the talks that will continue on Wednesday.

Hassan Rouhani, Iran’s president, who struck the original deal, used a speech over the weekend to praise his country’s nuclear “achievements”.

Iranian authorities have boasted that their nuclear capability is higher now than it was before the 2015 nuclear deal. Enrichment capacity has risen more than 20 per cent this year and Iran also has a significantly larger stockpile of enriched uranium, nuclear authorities said.

This moves Iran closer to an ability to enrich to weapons-grade, which is the main concern for western states and Iran’s regional rivals. Iran denies it has any intentions to pursue atomic weapons and say its nuclear ambitions are purely civilian.

Iran accused Israel of involvement in an explosion at Natanz last July, as well as the killing of its top nuclear scientist Mohsen Fakhrizadeh in November. Israel’s intelligence minister said at the time of the killing that he did not know who was behind the killing.

The Islamic republic also said an Iranian container ship was targeted by a “terrorist attack” in the Mediterranean Sea in March and another vessel was hit by an explosion in the Red Sea the following month.

Israel alleged that Iran targeted an Israeli-owned ship by an explosion in the Gulf of Oman in February. Iran has denied involvement.