The U.N. International Atomic Energy Agency, which regularly inspects Iranian nuclear sites including Fordow, had no immediate comment.

Iran has accused Israel and the United States of trying to sabotage its nuclear programme with cyber attacks and assassinations of its nuclear scientists. Washington has denied any role in the killings while Israel has declined to comment.

(Additional reporting by William Maclean and Marcus George in Dubai, Justyna Pawlak in Brussels, Fredrik Dahl in Vienna; Writing by Mark Heinrich; Editing by Robin Pomeroy)