Officials say a Russian drone has blasted a hole in an apartment building in northeastern Ukraine during a nighttime attack that killed at least six people and wounded nine others.

Ukraine has launched its second major drone attack in a week against Russian oil refineries hundreds of miles from its borders.

A Russian drone struck a multi-storey apartment building in the northeastern Ukrainian city of Sumy early on Thursday, killing nine people and injuring 13, including a child, President Volodymyr Zelenskiy said.