The army bolstered positions near the front line.
Pro-Russian separatists used weapons banned by the peace accord as they shelled government troops 86 times in the past 24 hours, killing one soldier and injuring seven more, the Defense Ministry said Monday.
President Petro Poroshenko said elite marine units had been sent to reinforce the nearby Sea of Azov port city of Mariupol.
The rebels said fighting hadn’t worsened.
“The past 24 hours has been marked by a significant intensification in the fighting,” military spokesman Colonel Andriy Lysenko told a briefing in Kiev, according to a video link.
Ukraine’s more-than-yearlong conflict, which has poisoned ties between Russia and its former Cold War foes, has threatened to reignite several times since the peace accord.
While unrest had eased, recent spates of violence have prompted phone calls between the leaders of Ukraine, Russia, Germany and France, which brokered the deal.
Issues including autonomy for the rebel regions and local elections remain thorny.
Having invaded and annexed Ukraine’s Black Sea peninsula of Crimea in March 2014, Russia now backs its neighbor’s territorial integrity, Prime Minister Dmitry Medvedev said Monday.
He discussed the Ukrainian conflict with his Slovenian counterpart, who called for an end to European Union sanctions against Russia because they harm trade.
The latest fighting has affected civilians districts, with a man and a woman wounded in the Donetsk region on Sunday.
Two civilians were also hurt on territory outside of government control, deputy rebel commander Eduard Basurin said by phone from Donetsk, alleging that the army is using arms banned under the truce.
“We aren’t observing the intensification of fighting that the Ukrainian side is talking about,” he said Monday.
“The number of attacks isn’t declining -- they continue firing at residential quarters.”
While the violence is worsening Ukraine’s recession -- a chemical plant owned by billionaire Rinat Akhmetov’s Metinvest BV was damaged in overnight shelling -- government bonds rallied.
Dollar-denominated debt due 2017 advanced to 55.7 cents on the dollar from 55.2 Friday as debt-restructuring talks progress and the next payment from a bailout nears.