Iran on Monday denied a media report that it had increased uranium enrichment as part of its controversial nuclear programme.
The Islamic Republic has not enriched uranium with a purity level of more than 60 per cent.
National Atomic Energy Agency spokesman Behrouz Kamalvandi has said.
On Sunday, the Bloomberg news agency cited diplomats saying that the country had enriched uranium to 84 per cent.
Nuclear bombs require uranium enriched to some 90 per cent.
The Vienna-based International Atomic Energy Agency, IAEA, wrote on Twitter on Sunday evening that it was aware of such reports.
The agency did not elaborate on the accusations.
In 2015, Iran committed itself to restrict its nuclear programme as part of an international agreement.
In return, sanctions were lifted.
After the United States unilaterally withdrew from the pact under then-president Donald Trump, Tehran gradually reversed the restrictions.
Current efforts to restore the nuclear pact were not progressing.