The United Nations Atomic Agency has expressed serious concern about Iran’s failure to cooperate with its probe into undeclared nuclear material in the country.

According to an IAEA report that Iran has now accumulated enriched uranium at nearly eight times the limit of a 2015 deal and has for months blocked inspections at sites where historic nuclear activity may have occurred.

The report said the IAEA has questions as to the possible "use or storage of nuclear material at the two sites and that one of them "may have been used for the processing and conversion of uranium ore including fluorination in 2003.