Several people were injured in an explosion at a residential building in the Russian city of St Petersburg on Saturday, as local media reported that a drone had been detonated. Governor Alexander Beglow spoke only of an “incident” as he vowed to promised help to the residents of the flats that were damaged. Six people had sought medical help and a 92-year-old woman was taken to hospital, the authorities said. The explosion shattered some of the windows in the five-storey apartment building. Residents of the flats were being housed in a kindergarten and treated by psychologists, according to re…