ZAPORIZHZHIA, Ukraine (AP) — Russia has resumed pulverizing the Mariupol steel mill that has become the last stronghold of resistance in the bombed-out city. Ukrainian fighters reported the new barrage Monday. It came after a brief cease-fire over the weekend allowed the first evacuation of civilians from the plant. Meanwhile, a senior U.S. official warned that Russia is planning to annex large portions of eastern Ukraine this month and recognize the southern city of Kherson as an independent republic. In Mariupol, more than 100 people left the rubble-strewn Azovstal steelworks on Sunday for the Ukrainian-controlled city of Zaporizhzhia, about 140 miles (230 kilometers) to the northwest.