The hostilities have subsided since the September cease-fire, but fighting between Russia-backed separatists and government troops still continues across the front line.
In a new report released today, the UN human rights office said that the number of people killed in more than a year of fighting in the east has risen to more than 6,400 people.
Two civilians were killed and five injured in shelling yesterday, according to the Donetsk News Agency, a rebel mouthpiece.
Ukrainian military spokesman Andriy Lysenko in Kiev said three Ukrainian troops were killed in fighting and four injured in the past 24 hours.
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Two other Ukrainian soldiers were captured outside the village of Maryinka, according to Lysenko.
The UN high commissioner for human rights, Zeid Raad al-Hussein, said there are "alarming reports of summary executions by armed groups" and his office is "looking into similar allegations against Ukrainian armed forces."
He added that there are "horrific accounts of torture and ill-treatment in detention" by both sides.
The explosions, the OSCE said, were "consistent with heavy and light weapons fire" including tanks and large-caliber artillery that should have been withdrawn by now from the front lines in compliance with the cease-fire accords.