Ukraine war latest: Military reports advance in the south, says ‘biggest strike still ahead’
Key developments on June 20: * Russian forces attack first responders in Kherson Oblast, killing 1, injuring 7 * Ukrainian forces reportedly advance south as fierce fighting is ongoing * Evacuation in flooded Kherson Oblast finished, emergency service says * Biden: Threat of Russia using tactical nuclear weapons is 'real' * Budanov: Russian forces plant