Russian forces were attempting to extend and consolidate their hold on Ukraine's industrial city of Sievierodonetsk on Thursday, edging closer to claiming a big prize in their offensive in the eastern Donbas region.

But in a boost for Ukraine, locked in a grinding struggle against Russia's invading army, the United States announced a $700 million weapons package for Kyiv that will include advanced rocket systems with a range of up to 80km.

Russia accused the US of adding...