The Ukrainian army said Moscow was focusing its main efforts to prevent Ukrainian air forces from operating effectively.
Ukraine's military says Russia has been targeting airfields and infrastructure in the south and east of the country to try and stop the Ukrainian airforce from operating effectively.
Meanwhile Russian President Vladimir Putin has declared that "as in 1945, victory will be ours", drawing many comparisons between the Second World War and the conflict in Ukraine on the eve of Victory Day celebrations in Red Square.
Ukrainian authorities fear up to 60 people sheltering in a school in Luhansk region may have been killed in a Russian strike on the building. It comes as leaders of the G7 countries pledged to ban or phase out Russian oil imports to their countries.
**Follow events as they unfolded on Sunday in our live blog below. **