A day after President Vladimir V. Putin announced a call-up that could see 300,000 civilians swept into military service, thousands of Russians across the country had reportedly received draft papers and were being bundled into buses on Thursday for training — and soon, possibly, to the front lines in Ukraine.

In mountainous eastern Siberia, the Russian news media reported that school buses were being commandeered to move troops to training grounds, and teachers were writing “povestki,” or draft papers. Videos circulated on social media purporting to show new conscripts saying tearful goodbyes before boarding buses.

The call-ups reportedly began within hours of a recorded video announcement by Putin in which he raised the stakes in the war and escalated his confrontation with the West despite Russia’s humiliating setbacks on the battlefield. By declaring for the first time that Russian civilians could be pressed into service in Ukraine, Putin risked a public backlash but said the move was “necessary and urgent” because the West had “crossed all lines” by providing sophisticated weapons to Ukraine.

Officials said the call-up would be limited to people with combat experience.