KHARKIV, Ukraine — Ukrainian forces fought village by village Saturday to hold back a Russian advance through the country’s east, while the United Nations worked to broker a civilian evacuation from the last defensive stronghold in the bombed-out ruins of the port city of Mariupol.

North Korean leader Kim Jong Un has warned again that the North could preemptively use its nuclear weapons if threatened. His latest comments came as he praised his top army officials for a massive military parade in Pyongyang this week. State media reported Saturday that Kim expressed “firm will” to continue developing his nuclear-armed military so that it could “preemptively and thoroughly contain and frustrate all dangerous attempts and threatening moves, including ever-escalating nuclear threats from hostile forces, if necessary.” The parade on Monday came after a spate of missile tests that underscored Kim’s willingness to force the United States to accept the North as a nuclear power and remove crippling economic sanctions.

Officials say a tornado that barreled through parts of Kansas destroyed or damaged hundreds of homes and buildings, injured several people and left more than 15,000 people without power. In addition to wreckage from the tornado itself, three University of Oklahoma meteorology students traveling back from storm chasing in Kansas were also killed in a crash Friday evening. Authorities say more than 1,000 buildings were affected when a strong twister swept through Andover on Friday evening. In the daylight Saturday, emergency crews found a more widespread path of destruction than was earlier estimated. There were no fatalities or critical injuries from the twister itself, despite the widespread destruction.

LAS VEGAS — A massive drought-starved reservoir on the Colorado River has become so depleted that Las Vegas now is pumping water from deeper within Lake Mead where other states downstream don’t have access.

WASHINGTON — President Joe Biden is turning to a Cold War-era law to boost production of lithium and other minerals used to power electric vehicles, but experts say the move by itself is unlikely to ensure the robust domestic mining Biden seeks as he promotes cleaner energy sources.