LVIV, Ukraine (AP) – Ukrainian officials have defiantly rejected a Russian demand that their forces in Mariupol lay down arms and raise white flags in exchange for safe passage. Russian troops have surrounded and are barraging the strategic southern port city. Ukrainian officials say the Russian military hit an art school sheltering some 400 people only hours before offering to open two corridors out of Mariupol in return for the capitulation of its defenders. Fighting for Mariupol has been intense, even as the Russian offensive in other areas has floundered to the point where Western governments and analysts see the broader conflict grinding into a war of attrition. Shelling also continued in Kyiv as Russian forces work to surround the Ukrainian capital.