The fighting between Russia-backed separatist rebels and Ukrainian government troops in the country's industrial heartland eased after a truce was signed in February. But despite pledges to withdraw heavy caliber weapons from the front lines, both sides seem to be engaged in recent heavy fighting.
The conflict has killed an estimated 6,400 people since April 2014, according to the United Nations.
The rebel mouthpiece Donetsk News Agency said artillery fire killed three people in a front line town of Horlivka and two in the rebel capital of Donetsk. Ukrainian officials reported two civilian deaths on their side, in a suburb of Mariupol on the Black Sea. The Ukrainian Security and Defense Council also reported two troops killed and six injured overnight.
The shelling on Monday came after failed talks between Ukraine, the rebels and the Organization for Security and Cooperation in Europe which were supposed to agree on further steps to withdraw weaponry.
An Associated Press reporter in Donetsk witnessed weaponry on the move in the past few days while salvos of incoming and outgoing Grad rockets were frequently heard.
President Vladimir Putin, who met representatives of various ethnic communities in the Russia-occupied Crimea on Monday, did not comment on the recent shelling. But he used the opportunity to claim that the current Ukrainian government is not free to make its own decisions because the country "is being managed from the outside."
Putin has alleged that Kiev's decisions are heavily influenced by Western powers including the United States.
Russian Foreign Minister Sergey Lavrov on Monday accused the Ukrainian government in Kiev of derailing the recent talks on withdrawal. Lavrov said the uptick in shelling could be the beginning of a new Ukrainian offensive.
"We're worried about events of the recent days, which look very much like preparation for fresh hostilities," he said.
OSCE observers warned Saturday about heavy weaponry that has gone missing after it was withdrawn from the front lines. The OSCE monitors were denied access to two locations in rebel-held areas where heavy caliber weapons were supposed to be kept. They were told at one location that 11 Grad multiple rocket launchers had been taken to Donetsk.