SAINT PETERSBURG-Schools, shopping malls and the Academy of Fine Arts in Saint Petersburg were evacuated on Friday after a fresh wave of fake bomb alerts that have spread chaos in Russia since September and whose origin is still unknown.

Around 20 “schools from different districts of Saint Petersburg were evacuated after bomb alerts,” the police of Russia’s second city said on Friday, the day of a visit by President Vladimir Putin. Local press and social media also reported the evacuations of several shopping malls, the Academy of Fine Arts, the State Institute of Cinema and Television and other university buildings. In early November, Moscow’s Bolshoi Theatre and the GUM and TsUM luxury department stores were evacuated following bomb alerts along with two top hotels near Red Square in the heart of the capital. Friday’s alerts were reminiscent of a series of phone-in false alarms in September that affected a total of 1.4 million people. No bombs were found at any of the venues mentioned. According to the FSB security service, those calls were made by Russian citizens outside the country.

Russia beefed up security measures after an underground train bombing in Saint Petersburg in April which left 16 people dead, including the attacker, and many more injured.