A drone attack damaged an apartment building in St Petersburg Saturday morning, according to Russian state news agency RIA Novosti.
Six people received medical help after the explosion rocked the building, the agency said, citing the press service of the city's health care committee.
The Mash news site said that the apartment building was hit by a Ukrainian drone. The Associated Press could not verify this claim.
The site published videos appearing to show the moment the apartment building was struck, showing a strong flash of light engulfing one side of the building and fragments of debris flying into the air. Another video showed car alarms going off.
Russia's Defence Ministry has not commented on the incident.