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 additional mines at Zaporizhzhia Nuclear Power Plant Russian overnight drone attack targets infrastructure in Lviv, Zaporizhzhia oblasts Ukrainian forces are advancing on the southern front line as the summer counteroffensive continues, the military said on June 20.