Ukraine urged its residents in the east of the country Thursday to take their "last chance" to flee mounting Russian attacks, after devastation around the capital Kyiv shocked the world.Six weeks after Russia invaded its neighbor, its troops have withdrawn from Kyiv and Ukraine's north and are focusing on the country's southeast, where desperate attempts are under way to evacuate civilians.The retreat from Kyiv revealed scenes of carnage, including in the town of Bucha, that Ukraine said were evidence of Russian war crimes, and which triggered a fresh wave of Western sanctions against Moscow.On Thursday, Ukrainian President Volodymyr Zelensky warned that Russia — which denies responsibility for the killings of civilians — was undeterred and continued "to accumulate fighting force to realize their ill ambitions in (eastern) Donbas.""They are preparing to resume an active offensive," he said, as officials in Donbas's Lugansk and Donetsk regions begged civilians to leave."These few days may be the last chance to leave," Lugansk regional governor Sergiy Gaiday wrote on Facebook, saying that all cities in the region were under fire and one person had died in the town of Kreminna.Meanwhile the prospect of a negotiated end to the war seemed to fade as Russia accused Kyiv of changing its demands since face-to-face talks in Istanbul last month.Foreign Minister Sergei Lavrov said a new draft agreement from the Ukrainian side suggested they were not interested in peace.Ukrainian presidential adviser Mykhaylo Podolyak hit back on Twitter, saying that if Moscow wanted to show its readiness to talk, "it should lower the degree of hostility."Foreign Minister Mevlut Cavusoglu of Turkey, which hosted the discussions, said the images of bodies from Bucha and other areas had "overshadowed" what had been an "emerging positive atmosphere" in talks.'Nowhere to go'Gaiday said previously that more than 1,200 people had been evacuated from Lugansk on Wednesday, but that efforts were being hampered by artillery fire, with some areas already inaccessible. For those unable to leave, he said, tonnes of food, medicine and hygiene products were being delivered as part of a massive humanitarian effort.The head of the Donetsk Regional Military Administration said strikes had targeted aid points. "The enemy aimed directly there with a goal to destroy the civilians," Pavlo Kyrylenko wrote on Facebook. Large areas of Lugansk and the neighboring Donetsk region have been controlled since 2014 by pro-Russian separatists.Shells and rockets were also slamming into the industrial city of Severodonetsk, the easternmost city held by Ukrainian forces. "We have nowhere to go, it's been like this for days," 38-year-old Volodymyr told AFP, standing opposite a burning building in Severodonetsk.More than 11 million people have been displaced since Russia invaded on Feb.

24, with the stated aim to "demilitarize" Ukraine and support Moscow-backed separatists.It is currently believed to be trying to create a land link between occupied Crimea and the statelets in Donbas.'Weapons, weapons, weapons'Ukrainian forces are also regrouping for the offensive, including on a two-lane highway through the rolling eastern plains connecting Kharkiv and Donetsk.Trench positions were being dug, and the road was littered with anti-tank obstacles. "We're waiting for them!" said a lieutenant tasked with reinforcing the positions, giving a thumbs up.Western allies have already sent funds and weapons to help Ukraine.But Foreign Minister Dmytro Kuleba on Thursday made a fresh appeal for heavy weaponry, including air defence systems, artillery, armored vehicles and jets."My agenda is very simple.

It has only three items on it.

It's weapons, weapons, and weapons," he told journalists ahead of a meeting with NATO ministers in Brussels.'Brutality and inhumanity'The evacuation calls in eastern Ukraine are being fuelled by fears of fresh atrocities, after chilling discoveries in areas from which Moscow's troops have withdrawn.U.S.

President Joe Biden said "major war crimes" were being committed in Ukraine, where images have emerged in recent days of bodies with their hands bound or in shallow graves."Civilians executed in cold blood, bodies dumped into mass graves, the sense of brutality and inhumanity left for all the world to see, unapologetically," Biden said. In one of the worst affected towns, Bucha, some residents were still trying to learn the fate of loved ones, while others were hoping to forget. Tetiana Ustymenko's son and his two friends were gunned down in the street, and she buried them in the garden of the family home. "How can I live now?" she said.The Kremlin denies responsibility for any civilian deaths and President Vladimir Putin on Wednesday accused Ukrainian authorities of "crude and cynical provocations" in Bucha.But the German government pointed to satellite pictures taken while the town was still under Moscow's control, which appear to show bodies in the streets.Human rights groups say rape is also being used as a "weapon of war" in Ukraine.Officials have alleged that Russian troops are now trying to cover up atrocities elsewhere to prevent further international outcry, including in the besieged city of Mariupol.Sanctions 'not enough'Western powers have already pummelled Russia with debilitating economic sanctions and on Wednesday the United States unveiled further measures targeting Russia's top banks and two of Putin's adult daughters.Britain sanctioned two banks and vowed to eliminate all Russian oil and gas imports by the end of the year, while the European Union is poised to cut off Russian coal imports.On the diplomatic front, EU nations this week have expelled more than 200 Russian diplomats and staff, mostly for alleged spying.And the UN General Assembly will hold a vote later Thursday on excluding Moscow from the UN Human Rights Council — a proposal backed by G7 foreign ministers from Canada, France, Germany, Italy, Japan, Britain and the United States.But Zelensky has said the new sanctions were "not enough" and urged countries to completely cut off Russia's banks from the international financial system, and to stop buying the country's oil.