Kateryna Velnychuk was having an afternoon nap when an explosion shattered the windows of her ground-floor flat, spraying shrapnel that tore holes through her walls and cupboards.

A Russian guided bomb had exploded in the courtyard outside the five-storey Soviet-era building, killing a postman on his rounds. As her flat filled with thick, milky smoke, the 22-year-old turned to see blood pouring from her boyfriend Vladyslav's head.

"As we’ve been living ... in a state of war, there was no sense of fear in the moment,” Velnychuk said. "You just understand there was an explosion. The only thought in your head is ‘I hope we survive.’” As Russia has intensified its air campaign against Ukraine in the last month, hammering its energy infrastructure and urban areas, no major city has been harder hit than Kharkiv.