Iran on Tuesday said it had enriched 6.5 kilograms of uranium to 60 per cent.
The announcement rattled the country's nuclear talks with world powers.
It marked another step by Tehran towards the nuclear weapons-grade enrichment of 90 per cent.
Anywhere between 12kg and 40kg of 90 per cent enriched uranium would be needed to make a bomb, depending on the sophistication of the device, according to the US Union of Concerned Scientists.
Iranian government spokesman Ali Rabiei was quoted by state media as saying the country had also produced 108kg of uranium enriched to 20 per cent purity, indicating quicker output than the rate required by the Iranian law that created the process.
Tehran said in April it would begin enriching uranium to 60 per cent, when it accused arch-foe Israel of sabotaging a key nuclear site.
At the time, the General Secretariat of the Arab League said it was "deeply concerned" by the plans.
Tuesday's disclosure came as Tehran and Washington held indirect talks in Vienna aimed at finding ways to revive a 2015 nuclear deal between Iran and world powers.
Iran's hardline parliament passed a law last year to oblige the government to harden its nuclear stance, partly in reaction to former US president Donald Trump's withdrawal from the nuclear deal in 2018.
Mr Trump's withdrawal prompted Iran to breach the limits imposed by the accord on its nuclear programme, designed to make it harder to develop an atomic bomb.
"Under parliament's law... the Atomic Energy Organisation was supposed to produce 120kg of 20 per cent enriched uranium in a year. According to the latest report, we now have produced 108kg of 20 per cent uranium in the past five months," Mr Rabiei was quoted as saying.
"In the area of 60 per cent uranium production, in the short time that has elapsed... about 6.5kg has been produced," Rabiei added.
A quarterly report on Iran's nuclear activities by the UN nuclear watchdog in May said that, as of May 22, Tehran had produced 62.8 kg of uranium enriched to 20 per cent.
It also had 2.4kg of uranium enriched to 60 per cent and more fissile material enriched to between 2 per cent and 5 per cent.
Tehran says it has no plans to make a nuclear weapon.