KYIV, Ukraine (AFP) — The World Health Organization has said Russia's missile attacks on Ukraine's power grid had left millions of lives at risk as the winter descended with frigid temperatures.

"This winter will be about survival," WHO regional director for Europe Hans Kluge warned on Monday saying it would be "life-threatening for millions of people in Ukraine."

Up to three million Ukrainians could leave their homes in search of warmth and safety, he said.

"They will face unique health challenges, including respiratory infections such as Covid-19, pneumonia, influenza, and the serious risk of diphtheria and measles in (an) under-vaccinated population," Kluge added.

Residents of Kherson were told that they can evacuate to other regions given the city's heavily damaged infrastructure and services.

Power company Yasno warned of extended blackouts.