Iran has played down a United Nations report that said Iranian nuclear scientists had enriched uranium to a higher-than-expected level.

On Friday, the International Atomic Energy Agency reported samples taken in February showed particles with enrichment levels of up to 27%, putting Iran closer to making potentially weapons-grade uranium.

The IAEA said it was assessing Iran's explanation that the traces of high-enriched uranium resulted from technical factors.

The sample came from Iran's Fordow facility, buried underground to shield it from air strikes.