welcome back, everyone. we are following the worsening situation in ukraine s mariupol. british intelligence says the majority of russian air-strikes in mariupol are likely being conducted using unguided free-falling bombs. and those weapons greatly increase the risk of civilian casualties as you see there from the ministry of defense. and this comes as mariupol s mayor says a third mass gravesite has been discovered. new satellite images purportedly shows freshly dug sites which have grown in size over time. the mayor says russian troops are forcing ukrainians to bury bodies in exchange for food. all this amid reports of increasingly dire conditions inside the steel plant. cnn s alex marquart has more. reporter: it s all that stands in vladimir putin s way from fully conquering mariupol. a key prize for the russians.