Authorities have evacuated St. Petersburg's Pulkovo Airport and suspended all flights after an anonymous bomb threat, Interfax reported.
An unknown caller telephoned the airport around 6 a.m. Friday to say that a bomb had been planted at the airport, the report said, citing the police.
Police immediately began evacuating passengers and airport personnel from the airport's two terminals and are now using sniffer dogs to look for explosives.
"The arrivals and departures of aircraft have been suspended," police said in a statement carried by Interfax.
It was not immediately clear when flights might resume.
Pulkovo is the third-busiest airport in Russia, after Moscow's Sheremetyevo and Domodedovo airports.