Russia has stepped up night time aerial attacks over the past week ahead of a renewed Ukrainian counteroffensive.

Ukrainian emergency services issued air raid alerts for Kyiv and most of central and eastern Ukraine early on Tuesday, extending from Vynnitsya in the west to all eastern regions and south to Kherson and the Odesa region on the Black Sea, the Reuters news agency reported.

At least four people were killed in drone and missile attacks in the early hours of Monday morning.

Kyiv is gearing up for a new counteroffensive to retake lands occupied by Russia, which continues to fight for the ruined eastern city of Bakhmut.

The United Nations has said at least 8,791 civilians have been killed since Russia launched its full-scale invasion of Ukraine in February last year. Thousands more have been wounded and millions forced from their homes.