Fierce fighting in east Ukraine over the past month has sent the death toll soaring, with at least 36 people killed every day, according to a UN rights report.

In four weeks alone, from mid-July to mid-August, at least 1,200 people were killed, more than double the total casualties in the conflict since it began in April, said the report by UN rights monitors to be released on Friday.

Ukrainian forces have over the past month made headway in their battle to flush out pro-Moscow separatists, regaining control of towns in the east and tightening their blockades around rebel strongholds.

"As a result of the intensified hostilities, there has been an escalation in the number of casualties which has more than doubled in total since the last report" in July, said the 39-page document obtained by AFP.

The one-month death toll of 1,200 did not include the 298 dead from the July 17 downing of Malaysia Airlines Flight MH17.

Since April, a total of 2,220 people have been killed, including 23 children.

The report implicitly blamed the separatists for the intensified killing, saying they were staging attacks from "densely populated areas, putting the civilian population at risk."

But it added that "responsibility for at least some of the resulting casualties and damage lies with Ukrainian armed forces" who have been shelling rebel positions in the cities.

Artillery, tanks, rockets and missiles have been used in the most recent rounds of fighting, with the front lines moving closer to the suburbs of the main city of Donetsk and Lugansk.

The report seemed to address Ukrainian claims that Russia is arming the rebels, saying that the separatists are "now professionally equipped and appear to benefit from a steady supply of sophisticated weapons and ammunition, enabling them to shoot down Ukrainian military aircraft such as helicopters, fighter jets and transport planes."

Ukraine has accused Russia of providing the weaponry that allowed rebels to shoot down Flight MH17, but Moscow denies the allegations. An investigation led by the Dutch government is under way.

The report also accused rebel fighters of committing murder, kidnappings, torture and other human rights violations.

At least 468 people remain in captivity, according to the report, the fifth issued by the UN rights monitoring mission.

UN Assistant Secretary General for Human Rights Ivan Simonovic is due to present the report during a visit to Ukraine on Friday.