The United Nations has released a damning report accusing Ukrainian forces and Russian-backed rebels of torturing and indiscriminately shelling civilians.
Its global governing body believes the eight-month conflict in the country's separatist east has killed at least 4634 and wounded 10,234 people.
However, Monday's survey suggests "the actual numbers of casualties is likely to be considerably higher".
And it said the lives of 5.2 million residents living in the devastated region were deteriorating further with the onset of winter and a complete breakdown of infrastructure that has left homes without water or heat.
The "situation is becoming extremely dire for the population, particularly older persons, children and people in institutional care, many of whom are on the brink of survival," the United Nations' human rights office said.
But the 27-page study was careful to assign blame for the humanitarian crisis to both the pro-Western government in Kiev and the mostly Russian-speaking insurgents who rose up in April against its rule.
"The efforts of the government to safeguard the territorial integrity of Ukraine and restore law and order in the conflict zone have been accompanied by arbitrary detentions, torture, and enforced disappearances of people suspected of 'separatism and terrorism'," the report said.
The United Nations said the guerillas in turn were guilty of creating a criminal state in parts of the industrial regions of Lugansk and Donetsk they control with the help of "foreign fighters" - a reference to Russian crack troops whose presence Moscow denies.
"As law and order increasingly broke down, so more human rights abuses, such as killings, torture, abduction for ransom and forced labour, started to be committed by members of armed groups, supported by increasing numbers of foreign fighters," said the report.
UN human rights envoy Ivan Simonovic said the guerillas were responsible for a larger share of the atrocities recorded by monitors who were first dispatched to the ex-Soviet republic during Russia's seizure of Crimea in March.
But UN officials also pointed to "limited progress" by Kiev in investigating more than 300 cases of indiscriminate shelling witnessed since the start of the year.
Ukrainian President Petro Poroshenko - elected in a snap May ballot following the downfall after months of street protests of a Moscow-backed leadership - has promised to examine allegations of abuses by his troops.
Rights groups believe some of the gravest crimes are being committed by Ukrainian ultra-nationalist volunteers who joined the fighting after taking an active part in last winter's popular uprising in Kiev.
The UN rights office believes 1357 people have been killed since the sides struck a Russian-brokered peace agreement on September 5 that only partially slowed the scale of bloodshed.
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