(CNN) An expert report from the Organization for Security and Cooperation in Europe (OSCE) found "clear patterns" of violations of international humanitarian law by Russian forces in Ukraine and detailed numerous incidents that it says could constitute war crimes.
The report says it found "credible evidence" suggesting violations of "even the most fundamental human rights (right to life, prohibition of torture and other inhuman and degrading treatment and punishment) have been committed, mostly in the areas under the effective control of Russia or entities under overall control of Russia."
In a statement at the OSCE on Wednesday, US Ambassador Michael Carpenter said that "taken as a whole, the report documents the catalog of inhumanity perpetrated by Russia's forces in Ukraine."
"The report is powerful in documenting the sheer scope of the Russian government's cruelty," Carpenter said.
The 110-page report details reports of targeted killings, torture, rape and forced disappearances.
The OSCE fact-finding mission "received several reports, sometimes accompanied by photographic evidence, alleging the use by Russian troops of the red cross emblem to mark military non-medical vehicles, of Ukrainian flags, army or police uniforms or vehicles, white flags, civilian clothes, and OSCE symbols to facilitate their military operations," it says.
It includes reports of a Ukrainian interpreter who was "held in captivity for nine days" by Russian forces. Left in an icy cellar, he was repeatedly beaten with an iron bar and rifle butts, tortured with electricity, deprived of food for 48 hours and subjected to a mock execution.
It includes the report of a woman who was raped multiple times, "in the presence of her small child," by a "drunken Russian soldier" who killed her husband.
"There are allegations of rapes, including gang rapes, committed by Russian soldiers in many other regions in Ukraine," the report states.
It cites the Human Rights Ombudsperson of the Ukrainian Parliament, who said that "500,000 civilians have been deported from Ukraine to Russia" and "that all of them had been forcibly displaced, first brought to some filtration camps in Russia near the Ukrainian border and that some of them were then brought as far as Sakhalin Island, but left there in freedom."
For many of the incidents, the report says they would constitute war crimes, but does not fully declare them as such. On the attack on the maternity hospital in Mariupol, however, it states: "This attack therefore constitutes a clear violation of (international humanitarian law) and those responsible for it have committed a war crime."
"While it may be that one hospital was used by the defender for military purposes or destroyed by mistake, it is hardly possible that this is the case when 50 hospitals are destroyed," the report states.
It notes the "particularly insidious form of attack" known as "double tap attacks" that Russian forces allegedly carried out in Kharkiv in early March. A Russian cruise missile hit the Kharkiv regional administration -- and a second strike hit the building after rescuers arrived several minutes later.
The report was the result of a three-week-long fact-finding mission by the three OSCE experts, and covers the time period from the start of the war on February 24 to April 1. That mission was launched after 45 countries triggered the OSCE's Moscow Mechanism, which is used to look into allegations of human rights abuses.
The report notes that the experts faced a number of limitations -- time and resource constraints, lack of access to Ukraine -- so "a detailed assessment of most allegations of IHL violations and the identification of war crimes and crimes against humanity concerning particular incidents has not been possible."
However, "it is not conceivable that so many civilians would have been killed and injured and so many civilian objects, including houses, hospitals, cultural property, schools, multi-story residential buildings, administrative buildings, penitentiary institutions, police stations, water stations and electricity systems would have been damaged or destroyed if Russia had respected its (international humanitarian law) obligations in terms of distinction, proportionality and precautions in conducting hostilities in Ukraine," it notes.
The report did not cover the time period when developments like the atrocities in Bucha came to light, which it says "require serious national and international enquiries, on the spot, with forensic experts." It states that "if confirmed, such killings would constitute egregious violations of (international humanitarian law) and war crimes."
The report says that "violations occurred on the Ukrainian as well as on the Russian side."
"The violations committed by the Russian Federation, however, are by far larger in nature and scale," it adds. Most of the reported violations by Ukraine are related to the treatment of Russian soldiers.
The report also notes that Russia, which is a member of the OSCE, did not give additional information to the fact-finding mission, and instead "referred the Mission to the official statements and briefings of the Government of the Russian Federation, which made it impossible for the Mission to take account of the Russian position on all pertinent incidents, except based on official open sources and websites."
"The Permanent Representation of the Russian Federation informed the Mission upon request that it considered the Moscow Mechanism largely outdated and redundant," the report said.
The OSCE report welcomed the work being done by other organizations -- the International Criminal Court (ICC), the United Nations, the International Court of Justice (ICJ) -- to investigate the crimes being committed in Ukraine.
"More detailed investigations are necessary, in particular with regard to establish individual criminal responsibility for war crimes," it states.
Carpenter, the US Ambassador to the OSCE, told reporters that "the information and evidence that was collected by the fact finding mission ... will be shared with other jurisdictions, such as the ICC and the ICJ. It can also be shared with national courts that may claim jurisdiction."
Carpenter did not rule out the possibility that the Moscow Mechanism could be triggered to look into further reports of atrocities being committed in Ukraine.
This story has been updated to include additional details.