Tosno is a town and the administrative center of Tosnensky District in Leningrad Oblast, Russia, located on the Tosna River, 53 kilometers …Tosno is a town and the administrative center of Tosnensky District in Leningrad Oblast, Russia, located on the Tosna River, 53 kilometers southeast of the center of St. Petersburg. Population: 39,101 ; 38,683 ; 32,459.