MOSCOW (AP) — Officials in Moscow say the Russian capital has faced over 500 fake bomb calls in two months and suffered a loss of millions of dollars as a result.

A slew of fake bomb threats has affected dozens of Russian cities since early September. Among those targeted by the bomb calls have been all Moscow airports, railway stations, shopping malls, banks, hotels, schools and administrative buildings. No explosives have been found following the anonymous calls.

Vladimir Chernikov, the head of security department in the Moscow city government, said Tuesday over 250,000 people were evacuated after 564 anonymous bomb warnings between Sept. 11 and Nov. 9.

Russia's top domestic security agency (FSB) has said several Russians living abroad were behind the calls, but it wouldn't identify them or describe their motives.