Russia bombarded Ukraine’s second-largest city with massive strikes in the early hours of Saturday, its mayor said, one night after Moscow carried out one of the war’s largest aerial assaults on Ukraine.

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.

Technological advances have given threadbare militaries and rebel fighters the ability to strike stunning blows against far stronger forces.

Russian ballistic missiles have been launched toward Ukraine from multiple directions, the Ukrainian Air Force said on Telegram Friday.

Air defense has been activated in Kyiv amid reports of airstrikes targeting Chernihiv, a city in northern Ukraine, ABC News confirmed.

President Trump said during his phone call with Vladimir Putin that he compared the war in Ukraine to a fight among children, suggesting they ‘fight for a while.’ Trump also said he warned Putin not to retaliate against Ukraine over its recent drone attack on Russian bombers.

President Trump spoke with Russia's Vladimir Putin yesterday, who vowed strong retaliation for Ukraine’s drone attacks deep inside Russia. NBC News’ Keir Simmons reports more. Igor Novikov, former Advisor to Ukrainian President Zelenskyy,

Donald Trump says Ukraine gave Putin 'a reason to bomb the hell out of them'. Asked about Russia's most recent attack on the Ukrainian capital Kyiv in the early hours of Friday that killed at least six people,