"The aggressor attacked the Fordo nuclear site again," Tasnim news agency reported, quoting a spokesperson for the crisis management authority in Qom province where the site is located.

The latest attacks come a day after the United States launched unprecedented strikes on Iranian nuclear facilities including Fordo and sites at Isfahan and Natanz.

US President Donald Trump said the strikes had "obliterated" Iran's nuclear capabilities, but other officials said it was too soon to assess the true impact on Iran's nuclear programme.

Iran condemned the attack and vowed retaliation, noting there were "no signs of contamination" after the US strikes.

The US strikes came around 10 days after Israel launched an attack on Iran killing nuclear scientists, top military commanders as well as striking military bases, nuclear sites and residential areas across the country.