Artillery fire intensified as night fell with more civilian deaths reported. At least 15 people have died since the fighting around Avdiivka and Donetsk intensified in the last five days.
Government troops and Russia-backed separatists continued fighting into Thursday night with shelling appearing to intensify after night fell.
Two civilians were reported to have died in the government-held industrial town of Avdiivka just north of Donetsk, and one in Donetsk city, the largest rebel-controlled city.
The head of the Ukraine-controlled Donetsk regional administration, Pavlo Zhebrivsky, said a humanitarian aid point in Avdiyivka had been hit by mortars late on Thursday. "According to preliminary figures, one person has been killed and one wounded in the attack. Shelling continues," he said on Facebook, blaming Russia-backed rebels for the attack.
Monitors from the Organization for Security and Cooperation in Europe (OSCE) have recorded frequent use of heavy weapons banned by the Minsk peace agreements.
During a visit to Hungary, Russian President Vladimir Putin accused Ukraine of starting the latest escalation to rally support from the new US administration. "The Ukrainian leadership needs money, and the best way to get the EU, the US and international organizations to pay is by posing as a victim of aggression," Putin said in Budapest on Thursday after a meeting with Hungarian Prime Minister Viktor Orban.
Damage from the fighting has cut power and water supplies to thousands of residents. Freezing winter temperatures have prompted warnings of a potential humanitarian crisis from aid agencies. The International Committee of the Red Cross in Ukraine called for all sides to hold fire to allow the emergency repair work to be carried out on damaged utilities.
There has been "a dangerous intensification of the conflict" between government and rebel forces in eastern Ukraine in the last days, Undersecretary-General Jeffrey Feltman told the UN Security Council on Thursday. He said the damage raises "serious concerns about possible violations of international humanitarian law by all sides."
European Union President Donald Tusk said "the fighting must stop immediately. The cease-fire
must be honored. Russia should use its influence to disengage the Russian-backed separatists."
The clashes have come as Kyiv works to persuade the US and EU to maintain economic sanctions against Russia linked to its involvement in the conflict and annexation of Ukraine's Crimea region.
US Ambassador to the UN Nikki Haley on Thursday condemned Russia's "aggressive actions" in Ukraine and pledged strong US support to Kyiv. "Until Russia and the separatists it supports respect Ukraine's sovereignty and territorial integrity, this crisis will continue," Haley told the Security Council.
kbd/jm (AFP, AP)