Global outrage spread on Monday at civilian killings in north Ukraine, including evidence of bound bodies shot at close range and a mass grave found in areas retaken from Russian troops, as fighting raged on in the countrys south and east. Taras Shapravskyi, deputy mayor of Bucha, a town around 40 km (25 miles) northwest of Kyiv city, said 50 of some 300 bodies found after Kremlin forces withdrew late last week were the victims of extra-judicial killings carried out by Russian troops. Ukrainian authorities said they were investigating possible war crimes there, a description also used by French President Emmanuel Macron. The Kremlin categorically denied any accusations related to the murder of civilians in the town. Reuters could not independently verify the number of dead or who was responsible. But its reporters in Bucha saw one man sprawled by the roadside, his hands tied behind his back and a bullet wound to his head. A mass grave at a church remained open, with hands and feet poking through red clay heaped on top. Pictures of the destruction and civilian deaths in Bucha looked set to galvanize the United States and Europe into fresh sanctions against Moscow. The images were also poised to overshadow peace talks between Russia and Ukraine, due to restart by video link on Monday against a backdrop of artillery bombardments in Ukraines south and east, where Russia says it is now focusing its operations after withdrawing from around Kyiv. Ukrainian television showed smoking fuel tanks and fire trucks near the Black Sea port of Odesa. Russia said it had destroyed an oil refinery used by the Ukrainian military. In Mariupol, another strategic southern port that has been under siege and shelled for weeks, the skeletal remains of residential tower blocks and other buildings surrounded by white cement dust and debris dominated the skyline, Reuters images showed. Ukraine says it has evacuated thousands of civilians in recent days from the city, a main target for Russias current offensive and surrounded by areas in the hands of Russian-backed separatists in the Donbas region. Ukraine was preparing for what its general staff said were about 60,000 Russian reservists called in to reinforce the offensive there, while British military intelligence also said Russian troops, including contractors from the Wagner private military company, were moving to the east. Reuters could not independently confirm the claims. Reuters correspondents saw convoys of armored vehicles belonging to pro-Russia forces near Mariupol. Sanctions on Russian energy? German Chancellor Olaf Scholz said Russian President Vladimir Putin and his supporters would "feel the consequences" of events in Bucha. Western allies would agree on further sanctions against Moscow in coming days, he said, though it was not clear how quickly a new package could come together or if it would included Russian energy exports. Germanys Defense Minister Christine Lambrecht said the European Union must discuss banning Russian gas - a departure from Berlins prior resistance to that idea. Frances Macron said new sanctions were needed, including on oil and coal, and there were very "clear clues pointing to war crimes" by Russian forces. US Secretary of State Antony Blinken described the images from Bucha as "a punch in the gut," while United Nations Secretary-General Antonio Guterres called for an independent investigation. The UN Security Council will discuss Ukraine on Tuesday but will not meet on Monday as requested by Russia, said Britains mission to the United Nations, which holds the presidency of the 15-member council for April. Moscow has said killings in Bucha there were "staged" to sully Russias name, and Kremlin spokesperson Dmitry Peskov said on Monday that its diplomats would press on with efforts to convene a Security Council meeting to discuss what Moscow has called "Ukrainian provocations" in the town. The facts and chronology did not support Ukraines version of events there, Peskov told reporters on a conference call, urging international leaders not to rush to judgment. Russia has previously denied targeting civilians and has rejected allegations of war crimes in what it calls a "special military operation" aimed at demilitarizing and "denazifying" Ukraine. Ukraine says it was invaded without provocation. The enemy will destroy everything Human Rights Watch said it had documented "several cases of Russian military forces committing laws-of-war violations" in the Ukrainian regions of Chernihiv, Kharkiv and Kyiv. Ukraines foreign minister called on the International Criminal Court to collect evidence of what he called Russian war crimes. The foreign ministers of France and Britain said their countries would support any such probe. However, legal experts say a prosecution of Putin or other Russian leaders would face high hurdles and could take years. Asked whether Putin would be held accountable for the civilian killings, Ukraines President Volodymyr Zelenskiy told CBS "Face the Nation" news program: "I think all the military commanders, everyone who gave instructions and orders should be punished." Shelling hit the eastern city of Kharkiv on Sunday causing seven deaths and dozens of injuries, local prosecutors said. The Odesa city council said "critical infrastructure facilities" were hit in the latest attack. Serhiy Gaidai, the governor of eastern Luhansk region, said Russia was building up forces to break through Ukrainian defenses. "I am urging residents to evacuate. The enemy will not stop, it will destroy everything in its path," he said in comments carried on Ukrainian television. Ukrainian officials were in talks with Russia to allow several Red Cross buses to enter Mariupol, Ukrainian Deputy Prime Minister Iryna Vereshchuk said. The charity abandoned earlier attempts due to security concerns. Russia blamed it for the delays.