Iran began enriching uranium up to 60 per cent purity Friday, its highest level ever, after an attack targeted its Natanz nuclear site, the country's parliament speaker said.
The comment by Mohammad Bagher Qalibaf, quoted by state television, did not elaborate on the amount Iran planned to enrich.
However, it is likely to raise tensions even as Iran negotiates with world powers in Vienna over a way to allow the US back into the agreement and lift the crushing economic sanctions it faces.
The announcement also marks a significant escalation after the sabotage that damaged centrifuges, an attack this past weekend suspected of having been carried out by Israel.
While Israel has yet to claim it, the country is widely suspected of having carried out the still-unexplained sabotage at Natanz, Iran's main enrichment site.
"The will of the Iranian nation is a miracle-maker and it will defuse any conspiracy," state television quoted Qalibaf as saying. He said the enrichment began just after midnight Friday.
The move could inspire a further response from Israel amid a long-running shadow war between the nations.
Israeli Prime Minister Benjamin Netanyahu has vowed never to allow Tehran to obtain a nuclear weapon and his country has twice preemptively bombed Mideast nations to stop their atomic programmes.