Ukraine war live updates: U.S. brushes off Putin's 'nuclear war' threat; Ukraine's forces shelling nuclear plant, Russia claims

This is CNBC's live blog tracking developments on the war in Ukraine. See below for the latest updates. 

The White House said it had no reason to adjust the U.S.' "nuclear posture" after comments by Russian President Vladimir Putin Wednesday in which he said his country was "technically" ready for nuclear war.

In other news, Russian-installed officials at the Zaporizhzhia nuclear power plant in southern Ukraine accused Ukraine's armed forces of shelling critical infrastructure at the plant on Thursday.

On Thursday, officials at the site said the plant had been shelled and that an explosive device was dropped into an area where tanks with diesel fuel were located, adding that the action could have had "dire consequences."

Russia has occupied the plant since March 2022, with the nuclear facility being a focal point of tensions and skirmishes between Ukrainian and Russian forces. CNBC was unable to verify the latest claims.

Russia has launched "massive" drone and artillery strikes against Ukraine overnight, Ukrainian officials said, with civilian infrastructure targeted in the northeast, east and south of the country.

The strikes come after a sharp uptick in Ukrainian drone and missile attacks against Russian regions over the last few days, with a number of major Russian oil refineries targeted and disrupting production.

Oleh Synehubov, the governor of the eastern border region of Kharkiv, said on Telegram on Thursday morning that Russia had carried out "massive" attack using drones, or UAVs (unmanned aerial vehicles), on television infrastructure in the region, with restoration work ongoing.

"About 15 settlements of the Kharkiv region were hit by enemy artillery and mortar attacks," Synehubov said. There appeared to be