(Reuters) – Scores of Ukrainian civilians including women and children remained trapped on Thursday in underground bunkers at a steel works in the ruined city of Mariupol, although President Vladimir Putin said Russia was ready to allow them to leave safely. FIGHTING * Captain Sviatoslav Palamar, a deputy commander of Ukraine’s Azov Regiment, posted a video online which purported to be shot in Mariupol’s Azovstal steel works and said “Heavy, bloody fighting is going on.” * The Kremlin denied a Ukrainian claim that its forces were storming the plant and said humanitarian corridors were currentl…