Investigators from virtually a dozen nations combed bombed-out cities and freshly dug graves in Ukraine on Wednesday for proof of battle crimes, and a wide-ranging investigation by a world safety group detailed what it stated had been “clear patterns” of human rights violations by Russian forces.

Among the atrocities might represent battle crimes, stated investigators from the Group for Safety and Cooperation in Europe, who examined myriad reviews of rapes, abductions and assaults on civilian targets, in addition to using banned munitions.

On Wednesday, civilians had been nonetheless bearing a lot of the brunt of the seven-week-old invasion as Russian forces, massing for an assault within the east, bombarded Ukraine’s second-largest metropolis, Kharkiv, placing an residence constructing.

In an hourlong telephone name with Volodymyr Zelensky, Ukraine’s chief, President Biden stated america, already a serious supplier of defensive armaments to Ukraine, would ship a further $800 million in navy and different safety support. The package deal will embrace “new capabilities tailor-made to the broader assault we count on Russia to launch in jap Ukraine,” Mr. Biden stated in an announcement.

American officers stated Wednesday that america, in serving to Ukraine put together for such an assault, had elevated the movement of intelligence to Ukraine’s authorities about Russian forces in jap Ukraine and the Crimean Peninsula, which Russia seized from Ukraine eight years in the past. The administration is also contemplating whether or not to ship a high-level official to Kyiv, Ukraine’s capital, within the days forward as an indication of assist for the nation, in response to an individual accustomed to the inner discussions.

Warfare crimes claims are famously tough to research, and nonetheless tougher to prosecute. It’s uncommon for nationwide leaders to be charged, and even rarer for them to finish up within the defendant’s chair.

However the battle in Ukraine might show completely different, some consultants say, and momentum has been constructing to carry the Kremlin management accountable.

An Worldwide Felony Courtroom investigation into attainable battle crimes has been underway since final month, and quite a few nations have been methods for the United Nations to assist create a particular courtroom that might prosecute Russia for what is called the crime of aggression. Different potentialities embrace making an attempt Russians within the courts of different nations underneath the precept of common jurisdiction, the authorized idea that some crimes are so egregious they are often prosecuted anyplace.

A part of the motivation for accountability is the revulsion in Europe and far of the world over the habits of President Vladimir V. Putin’s forces, together with reported executions of sure civilians and different atrocities.

Warfare crimes consultants additionally level to technological advances in forensic instruments like facial identification software program not out there to these trying into earlier conflicts, and the sheer variety of investigators on the bottom in Ukraine — crucially, with the federal government’s blessing. A dozen French investigators joined the inquiries this week.

“There will likely be prosecutions, and doubtless everywhere in the world,” stated Leila Sadat, a world regulation professor at Washington College in St. Louis, and a longtime adviser to the chief prosecutor of the Worldwide Felony Courtroom on crimes towards humanity. “Ukraine is definitely crawling with battle crimes investigators proper now.”

Nonetheless, consultants warned that the method could be sluggish, and that any early indictments would most probably be towards lower-ranking Russian officers and armed-service members. Russia, which has described the accusations as fictional or unfounded, will not be anticipated to cooperate in any prosecution.

The report launched Wednesday by the Group for Safety and Cooperation in Europe, a 57-member group primarily based in Vienna that features Russia, Ukraine and america, is without doubt one of the first in-depth research of human rights abuses throughout Russia’s offensive towards Ukraine.

Investigators checked out among the most infamous assaults and different violent acts of the battle, together with Russia’s bombings of a theater and a maternity hospital within the besieged metropolis of Mariupol, each depicted within the report as obvious battle crimes.

Additionally they pored via accounts of different horrific, if much less seen, acts of violence. “There are allegations of rapes, together with gang rapes, dedicated by Russian troopers in lots of different areas in Ukraine,” they wrote.

However usually, they had been stymied.

Russia declined to cooperate with the three-person staff of investigators, making it “unimaginable for the mission to take account of the Russian place on all pertinent incidents,” the report stated.

Investigators discovered that Ukrainian forces, too, had been responsible of some abuses, notably within the remedy of prisoners of battle. “The violations dedicated by the Russian Federation, nevertheless, are by far bigger in nature and scale,” their report stated.

Michael Carpenter, the American ambassador to the O.S.C.E., stated the report “paperwork the catalog of inhumanity perpetrated by Russia’s forces in Ukraine.” The European Union issued a equally optimistic appraisal.

“This battle will not be solely fought on the bottom,” the bloc stated in an announcement. “It’s clear that the Kremlin can be waging a shameful disinformation marketing campaign with a purpose to disguise the info of Russia’s brutal assaults on civilians in Ukraine. Dependable data and assortment of info have subsequently by no means been as essential as as we speak.”

The Kremlin’s personal mission to the O.S.C.E. dismissed the findings as “unfounded propaganda.”

On Tuesday, even because the Ukrainian authorities had been unearthing our bodies in full view of worldwide journalists and different observers, Mr. Putin referred to as the atrocities a “pretend” that had been elaborately staged by the West.

On Wednesday, standing close to the location of two mass graves, Ukraine’s prosecutor normal, Iryna Venediktova, stated there was an obligation each to uncover the info and to take action in a clear method to fight Russian disinformation.

“If you see lifeless our bodies right here, from the opposite facet, from the Russian Federation, they are saying it’s all pretend, all that is our theater,” Ms. Venediktova stated.

Ukrainian prosecutors and the newly arrived staff of French consultants exhumed our bodies this week from mass graves in Bucha, a Kyiv suburb, the place a whole bunch of civilians had been killed throughout the temporary Russian occupation of the realm. The French authorities stated that its staff included ballistics and explosives consultants and that it had the flexibility to do speedy DNA assessments.

Proof from the French investigation and others involving a number of completely different nations will likely be channeled to the Worldwide Felony Courtroom, which began trying into attainable battle crimes every week after the Feb. 24 invasion. Though Ukraine will not be a part of the settlement that created the courtroom 20 years in the past, it has granted the courtroom authority to research and prosecute on this battle.

Investigators say they’re intent on exhibiting the world the fact of the battle.

“They will see all the things. They will see the scenario right here: actual graves, actual lifeless our bodies, actual bomb assaults,” Ms. Venediktova stated. “That’s why for us this second is essential.”

The O.S.C.E. report described a variety of subterfuge by Russian forces, together with using Pink Cross emblems, white flags, Ukrainian flags and civilian garments. And the group’s investigators expressed concern that either side could be holding extra prisoners than disclosed.

On Wednesday, President Zelensky spoke immediately about one in every of them: Viktor Medvedchuk, a Ukrainian politician and ally of Mr. Putin’s who was detained this week. Mr. Zelensky proposed exchanging him for Ukrainians held captive by Russian forces.

At the same time as settlement grew amongst many world leaders that battle crimes expenses had been warranted, there was some disagreement over learn how to characterize Russia’s actions. Some leaders, amongst them Mr. Biden, have begun to make use of the time period “genocide” — an escalation of his rhetoric. On Wednesday, France’s president, Emmanuel Macron, dissented.

“What is occurring is insanity, it’s a brutality that’s unheard-of,” Mr. Macron stated. However, he stated, “Genocide has a that means. The Ukrainian individuals and the Russian persons are brethren individuals.”

“I’m undecided that an escalation of phrases serves the trigger,” he stated.

The battle crimes report got here amid indicators that Russia’s invasion might have backfired in a minimum of one respect. Mr. Putin has lengthy objected to NATO’s growth eastward into the onetime domains of the Soviet Union, describing it as a elementary risk to Russia. However on Wednesday, two militarily nonaligned nations, Finland and Sweden, stated they had been severely contemplating becoming a member of the alliance.

Authorized consultants didn’t rule out the likelihood, some day, of an indictment of Mr. Putin, who has already been castigated as a battle legal by some Western leaders. And had been Mr. Putin to be criminally charged by a courtroom exterior Russia, it will possible imply he must limit his worldwide journey with a purpose to reduce the danger of attainable arrest had been he to enterprise past Russia’s borders.

David Crane, a authorized scholar at Syracuse College who was the chief prosecutor for the Particular Courtroom for Sierra Leone, a world battle crimes tribunal that convicted the previous president of Liberia, Charles G. Taylor, stated he was assured that the Worldwide Felony Courtroom or another judicial physique would discover authorized grounds to cost the Russian president.

And even when Mr. Putin isn’t arrested and stays the chief of Russia, he stated, the authorized and diplomatic penalties of a battle crimes indictment would severely undermine his credibility.

It might be as if “there’s like an ash mark on his brow,” Mr. Crane stated. “There’s no good choices for him.”

Marc Santora reported from Warsaw, Erika Solomon from Berlin and Carlotta Gall from Bucha, Ukraine. Reporting was contributed by Jane Arraf from Lviv, Ukraine; Aurelien Breeden from Paris; Cora Engelbrecht from Krakow, Poland; Farnaz Fassihi from New York; Eric Nagourney from Los Angeles; and Rick Gladstone from Eastham, Mass.