Amnesty International says there is "mounting evidence" that both Ukrainian pro-government militia and separatist forces are responsible for war crimes in the country’s east, and accuses Russia of fueling the conflict.
Documenting incidents of "indiscriminate shelling, abductions, torture, and killings," the London-based organization urged all parties on September 7 to stop violations of the laws of war.
The statement was prepared before a cease-fire agreement was reached on September 5 after almost five months of fighting.
That uneasy truce appeared to be unraveling after shelling erupted in Mariupol and Donetsk.
Amnesty International’s Secretary General Salil Shetty said all sides were "blatantly violating" their international obligations.
Amnesty International Ukraine researcher Heather McGill told RFE/RL that they have shown "disregard" for civilian lives.
McGill spent two weeks recently in Ukraine speaking to internally displaced people, while other Amnesty researchers interviewed Ukrainian refugees in Russia's Rostov region, which abuts Ukraine.
Amnesty quoted the eyewitnesses as saying Ukrainian government forces subjected their neighborhoods to "heavy shelling."
Citing "credible reports" of abductions and beatings carried out by volunteer battalions operating alongside regular Ukrainian armed forces, Amnesty called on Ukrainian authorities to investigate the allegations and bring to justice those responsible for war crimes.
The group also quoted witnesses as saying pro-Russian separatist fighters “abducted, tortured, and killed their neighbors.”
On September 5, the New York-based group Human Rights Watch (HRW) urged insurgents to stop forcing civilians to work in "punishment brigades" and exposing them to dangers of the front lines, saying both were "serious violations of the laws of war."
Russia has repeatedly denied any involvement in the fighting in Ukraine.
But Shetty of Amnesty International urged Russia to stop the "steady flow of weapons and other support" to the insurgents, which she said are implicated in "gross human rights violations."
The human rights watchdog released satellite images that it said indicated a build-up of Russian armor and artillery in eastern Ukraine.
Amnesty International said the images show new artillery positions being established just inside the Ukrainian border on August 13-29, including "what appear to be 122-mm Howitzer D-30 artillery units in firing positions pointed toward the west."
Amnesty said the satellite imagery, reports of Russian troops captured inside Ukraine, and witness accounts of Russian troops and military equipment crossing the Ukrainian border provide evidence that the conflict has burgeoned into "an international armed conflict."
Meanwhile, McGill said, the civilian populations have been caught in the middle of the fighting.
She said people she talked to "didn't feel that either sides represented their views or that they had any voice in this [conflict] yet, [but] their homes are being destroyed."