When the air raid sirens sound at night, Svitlana Honcharova takes her two young sons to the cellar under their apartment in the Ukrainian city of Sumy and prays they will still be alive in the morning.

Although thousands have fled Russia's bombardment of Sumy in the far northeast, 31-year-old Honcharova dares not leave as she is stateless, meaning she is not recognized as a citizen of any country.

"I'm afraid that if I decided to leave I wouldn't be able to cross checkpoints or borders because I don't have documents," Honcharova told the Thomson Reuters Foundation in a video call.