By Pavel Polityuk and Simon Lewis KYIV/KONSTYANTYNIVKA, Ukraine (Reuters) -Fighting intensified on Saturday for Lysychansk, Ukraine’s last bastion in the strategic eastern province of Luhansk, while blasts shook a southern city after the civilian toll from Russian strikes climbed in towns well behind the frontlines. Andrei Marochko, an officer of the pro-Russian Luhansk People’s Militia, was quoted by Russia’s TASS news agency as saying that the militia’s red hammer-and-sickle flag was now flying over the administrative building in Lysychansk, although Ukraine’s military rejected claims that t…