Updates with new headline, Ukrainian military statementThe Ukrainian army retreated from the strategic city of Lysychansk Sunday as Russia claimed a major victory by seizing control of the entire eastern Luhansk region.The Ukrainian withdrawal followed weeks of fierce fighting and marked a decisive breakthrough for Moscow's forces more than four months after their invasion and after turning their focus away from the capital Kyiv.Lysychansk had been the last major city in the Luhansk area of the eastern Donbas region still in Ukrainian hands and frees up Moscow's forces to advance on Kramatorsk and Sloviansk in neighbouring Donetsk.President Volodymyr Zelensky had earlier denied Russian claims of Lysychansk's fall before the Ukrainian army announced the retreat on Sunday evening."The continuation of the defence of the city would lead to fatal consequences" in the face of Russia's superiority in numbers and equipment, the army said in a statement. "In order to preserve the lives of Ukrainian defenders, a decision was made to withdraw."Unfortunately, steel will and patriotism are not enough for success -- material and technical resources are needed."Russian Defense Minister Sergei Shoigu said earlier that Moscow's forces have taken the Ukrainian city of Lysychansk and control the entire Luhansk region, which has been the target of fierce battles in recent weeks."Sergei Shoigu has informed the commander in chief of the Russian armed forces, Vladimir Putin, of the liberation of the People's Republic of Luhansk," the defense ministry said in a statement quoted by Russian news agencies.Russian forces and their separatist allies have taken "full control of Lysychansk and other nearby towns, notably Belogorovka, Novodruzhesk, Maloryazantseve and Bila Hora," the statement said.Russia seized Lysychansk's twin city of Sievierodonetsk last week following weeks of intense fighting.