Russia launched a massive attack on Ukraine's Kharkiv, killing four and injuring dozens. President Zelenskyy condemned the violence and appealed for urgent air defense assistance.

The United States believes that Russian President Vladimir Putin's threatened retaliation against Ukraine over its drone attack last weekend has not happened yet in earnest and is likely to be a significant,

The attack on Friday, which killed at least four people nationwide, came two days after Russia vowed retaliation for an audacious drone assault on its strategic bomber bases.