MOSCOW, September 22. /TASS/. More than 1,000 buildings received hoax bomb threats across Russia this week and some 400,000 people were evacuated, a law enforcement source told TASS on Friday.

A wave of bomb calls in Russian cities began on September 11. "It affected 80 cities, including Moscow. More than 1,000 facilities were checked after hoax bomb alerts and some 400,000 people were evacuated," the source said.

Among the targeted facilities were shopping centers, administrative buildings, schools, passenger stations, airports, museums and night clubs. None of the threats have been carried out.

Police believe this was a planned action organized by a group of persons. The mass media offered various theories, from the so-called Ukrainian trace (like in 2014, when false bomb calls came from Ukrainian telephone numbers) to a theory that the Islamic State terrorist group is behind these bomb threats.