Donetsk , Ukraine ( CNN ) -- The battle for control of the eastern Ukrainian town of Slovyansk has intensified in the past 24 hours , with civilians caught in heavy crossfire between government forces and pro-Russian separatists . Each side blames the other for mortar and rocket fire that has struck apartment buildings and homes in the town , which is now also suffering acute power and water shortages . Social media video from Slovyansk uploaded Sunday and apparently filmed in the past two days shows extensive damage to an apartment block in the center of the town , which appears to have taken a direct hit to the third floor . Another building was engulfed by fire . Other videos showed people hurrying to basements , with the sound of artillery and rocket fire in the distance -- and at times much closer . The charred ruins of cars littered the streets , and windows in a number of buildings had been blown out . The office of President Petro Poroshenko , who was inaugurated Sunday in Kiev , said he had opened the first meeting of a three-party contact group on implementing a peace plan he had discussed with French President Francois Hollande , German Chancellor Angela Merkel and Russian President Vladimir Putin on the margins of the D-Day commemorations on Friday . In an apparent reference to the fighting around Slovyansk , Poroshenko said : `` We have to stop fire this week . For me , every day of people dying , every day of Ukraine paying such a high price is an unacceptable one . '' The talks involve Ukrainian ambassador to Germany Pavel Klimkin , a special envoy with the Organization on Security and Cooperation in Europe and Russian Ambassador to Ukraine Mikhail Zurabov , the President said . Slovyansk -- normally a city of some 130,000 people -- was taken over by separatists early in April . The Ukrainian army first attacked separatist blockades on its outskirts later that month but subsequently withdrew . Only in the past week have Ukrainian troops moved decisively to bottle in the separatists , using tanks , artillery and rockets against their defenses . A spokesman for the Anti-Terrorist Operation told CNN from outside Slovyansk that the army was not shooting at residential areas and that separatists had launched a counterattack early Sunday . Separatist officials in the town told the Russian news agency ITAR-TASS that artillery fire had been aimed at the city administration building , the former Security Service compound and Police Department -- all of which are occupied by the separatists . ITAR-TASS quoted a local militia official as saying that `` there were victims among civilians as many were injured by shrapnel . '' CNN was unable to confirm the account , but one social media video appeared to show a pool of blood close to the impact of a shell . Overall casualties in Slovyansk are impossible to quantify . A health official with the Donetsk regional administration , Elena Peteyaeva , said 140 bodies had been collected -- but it was not clear over what time span . Peteyaeva said there were only three ambulances at work in the town and very few people were able to get out . A CNN team that reached the area Thursday found all major roads into Slovyansk blocked and deserted . During an extensive tour of the region , only two cars , piled high with belongings , emerged from country tracks . South of Slovyansk , separatist groups have consolidated their hold of several towns in the Donetsk and Luhansk regions . A CNN team on Sunday visited Shnizhne , Krasny Luch and Antratsyt , all on or close to the main road east to the Russian border . Separatist roadblocks guarded the fringes of each town in a heavily industrial part of the Donbass region , and dozens of well-armed fighters were seen in the center of Shnizhne . The main administration building in Antratsyt was surrounded by sandbags . One nearby border crossing at Marynivka -- which was the scene of clashes last week when separatists of the so-called Vostok Battalion tried to bring heavy trucks and an infantry fighting vehicle across the border -- had been reinforced by the Ukrainian Border Guard , with additional troops deployed on nearby hills . Even so , the troops deployed at the border admitted it was impossible to patrol the 1,200-mile border effectively , much of it unfenced amid rolling , empty countryside . Journalists Azad Safarov and Victoria Butenko contributed to this report .
Civilians caught in a crossfire between Ukrainian troops and pro-Russian separatists . The United Nations says at least 5,400 people have been killed since the conflict began last April. President Petro Poroshenko has consulted with France , Germany and Russia on peace push . Poroshenko : ' Every day of Ukraine paying such a high price is an unacceptable one '