(Fixes spelling of Bondarev in second to last paragraph) By Pavel Polityuk and Natalia Zinets KYIV/MARIUPOL (Reuters) – Ukrainian President Volodymyr Zelenskiy told global business leaders on Monday the world must increase sanctions against Russia to deter other countries from using “brute force” to achieve their aims. Zelenskiy spoke via video link to the World Economic Forum in Davos as the Ukrainian military claimed to have held off a Russian assault on Sievierodonetsk, an eastern city that has become the main target of a Russian offensive after the surrender of the southern port city of Ma…