Austria rejected the visa application submitted for Mohammad Eslami, head of the Atomic Energy Organization of Iran, to attend the International Atomic Energy Agency conference in Vienna.
Eslami and his delegation had planned to travel to Vienna on Saturday but later returned to Tehran.
Iranian Foreign Ministry spokesman Esmaeil Baghaei said on Monday that he considered the visa decision "completely unjust." Baghaei said Iran had formally objected to the decision and that Austria's chargé d'affaires in Tehran had been summoned to the Foreign Ministry.
Baghaei also said pressure from the United States should not prevent host countries from fulfilling their obligations.