(Reuters) – Russian forces in Ukraine were blasting cities and killing civilians but no longer making progress on the ground, according to Western intelligence, while talks on ending the fighting resumed as the war entered its fourth week. CIVILIAN TOLL * Over 350,000 people are still sheltering in the besieged southern port of Mariupol and some 30,000 have left so far, officials said, as rescuers continued combing the rubble of a theatre bombed the previous day. Russia denies striking it. * The governor of the northern Chernihiv region said 53 civilians were killed there in bombardment over t…