Iran has begun 60% uranium enrichment at its Natanz plant, the country’s nuclear chief said on Friday, days after an explosion at the site that Tehran blamed on Israel.

“We are producing about nine grams of 60% enriched uranium an hour,” Ali Akbar Salehi, head of the Atomic Energy Organization of Iran, told state television.

“But we have to work on arrangements… to drop it to 5 grams per hour. But then we will simultaneously produce 20% (uranium),” Salehi said.

Earlier, parliament speaker Mohammad Baqer Qalibaf said Iranian scientists had successfully started enriching 60 percent uranium at 12:40 a.m. local time (2010 GMT).

“The will of the Iranian nation makes miracles that thwart any conspiracy,” Qalibaf said on Twitter.

In Vienna, a spokesman for the United Nations nuclear watchdog IAEA declined to comment on the Iranian statements about 60% enrichment.

Iran has said its decision to increase enrichment to its highest level ever was in response to sabotage at its nuclear site at Natanz on Sunday by Israel.

Iran and global powers are meeting in Vienna to try to rescue a 2015 nuclear deal abandoned by Washington three years ago, in an effort potentially complicated by Tehran’s decision to ramp up uranium enrichment.

The 2015 agreement sought to make it harder for Iran to develop an atomic bomb – something it denies ever trying to do – in return for lifting sanctions.

Abbas Araqchi, Iran’s chief nuclear negotiator at nuclear talks in Vienna, said on Tuesday that Iran would activate 1,000 advanced centrifuge machines at Natanz.

An Iranian official told Reuters that “60% enrichment will be in small quantity” only.

Multiple Israeli media outlets have quoted unnamed intelligence sources as saying the country’s Mossad spy service carried out the sabotage operation at the Natanz complex. Israel – widely believed to be the only Middle Eastern country with a nuclear arsenal – has not formally commented on the incident.