ODESA, Ukraine — Five days after an explosion at a Russian prison camp killed at least 50 Ukrainian prisoners of war, evidence about what happened remains sparse, but Ukrainian officials said on Wednesday that they were steadily compiling proof that the mass slaughter was a war crime committed by Russian forces.
At a background briefing for journalists in the capital, Kyiv, senior Ukrainian officials who spoke on the condition of anonymity outlined evidence to suggest that Russian forces appeared to be preparing for mass casualties in the days before the July 29 explosion.
Satellite images taken before the explosion, they said, show what appear to be freshly dug graves within the prison complex. A New York Times analysis of images from Maxar Technologies and Planet Labs confirms that some time after July 18 and before July 21, about 15 to 20 ground disturbances appeared on the southern side of the complex, roughly 6 to 7 feet wide and 10 to 16 feet long at first; some later appeared to have been lengthened and merged with each other. Whether they were graves is unclear.
In addition, a day before the explosion, Russian forces positioned near the camp had opened fire on Ukrainian troops in an apparent attempt to draw return fire, the Ukrainian officials said.
“Understanding that we would not return fire, they carried out a terrorist attack themselves,” one of the briefers said. “How they did this needs to be carefully studied.”
Ukrainian officials, along with independent analysts, have cautioned that assessments so far have been solely reliant on publicly available information, including video published by the Kremlin’s own news services, of the blast site near the town of Olenivka on Russian-controlled territory in Ukraine’s Donbas region. A lack of verifiable evidence has made drawing clear conclusions difficult, and the Russian government so far has refused to grant independent investigators access to the site.
The International Committee of the Red Cross, which has a mandate under the Geneva Conventions to inspect conditions in which prisoners of war are held, requested permission from the Russian government to access the site on the day of the explosion.
“As of yet, we have not been granted access to the POWs affected by the attack nor do we have security guarantees to carry out this visit,” the Red Cross said in a statement on Wednesday. Additionally, the organization said offers to donate supplies like medicine and protective gear have gone unanswered.
Russia’s defense ministry has claimed, without offering any verifiable evidence, that Ukraine’s own military used a highly sophisticated American precision-guided rocket system known as HIMARS to kill the Ukrainian troops.
Military analysts call that unlikely, but impossible to rule out with the available information.
The Russian video and the satellite pictures show evidence of a smaller blast than those typically caused by the HIMARS-fired rockets supplied to Ukraine. The rockets usually leave a crater, but none is evident in the images. The walls of the barracks and much of the interior are blackened but still intact, and there is no apparent damage to an adjoining building. The interior images show beds still upright and lined up in rows, inconsistent with the strong shockwave seen in other HIMARS strikes.
“There’s some evidence pointing away from a HIMARS. But that doesn’t mean that I know or you can tell from the evidence presented specifically what it was,” said Brian Castner, a weapons expert for Amnesty International. He added that “you need to leave open the possibility that a weapon of, you know, from either side fell short, misfired.”
Moscow at first said Ukraine had carried out the strike to dissuade others from surrendering and giving information to Russian interrogators. On Wednesday it offered a new explanation, as Colonel Gen. Alexander Fomin, deputy defense minister, said in a speech that Ukrainian officials had ordered the strike after Russia began publishing video interrogations of captured fighters admitting to attacks on civilians.
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“The Kyiv authorities seek to eliminate witnesses and perpetrators of their crimes against their own people,” General Fomin said.
Ukrainian and American officials have rebutted the Kremlin claims, and Ukrainian investigators have hypothesized that an explosive device was detonated inside the barracks. On Wednesday, Ukraine’s military intelligence agency issued a statement alleging that soldiers held at the prison had been tortured. Earlier, some officials had speculated that Russian forces had killed the prisoners to cover up evidence of abuse.
The murder of soldiers captured in battle would add to the host of apparent Russian war crimes since President Vladimir V. Putin ordered the invasion of Ukraine on Feb. 24. In the first months, Russian forces massacred civilians in bedroom communities outside of Kyiv. They bombed a maternity ward and a theater where civilians were sheltering in Mariupol on their path to leveling that coastal Ukrainian city. Russian rockets have hit apartment buildings, shopping malls, train stations, busy public squares and fleeing civilians.
In each case, Russian officials have denied the facts on the ground and spun baseless — and often contradictory — conspiracy theories in an attempt to deflect blame. In several cases, such as the bombing of a busy train station in Kramatorsk in April that killed 50 people, Russia has blamed its own attacks on Ukraine, asserting with no evidence that Ukraine is conducting so-called false flag operations to make Russia look bad.
No Russian guards were killed or wounded in the prison explosion in Olenivka, which appeared to leave other structures nearby undamaged.
Some of the prisoners killed were badly wounded soldiers slated to be swapped in a prisoner exchange expected to occur in the coming weeks, said Andrei Yusov, a spokesman for Ukraine’s military intelligence service. These soldiers “should have been in a hospital not in a barracks,” he said in a statement.
Nearly all of those killed were soldiers who had fought in the defense of Mariupol and surrendered in May after an 80-day siege at the sprawling Azovstal Iron and Steel Works.
In Ukraine, these soldiers have become war heroes, their likenesses seen on billboards throughout the country. The idea that Ukraine’s military would seek to kill them is beyond comprehension, said Maj. Mykyta Nadtochii, the commander of the Azov Regiment, a unit within Ukraine’s national guard whose fighters made up the majority of those killed at Olenivka.
“We understand what it means to be a prisoner,” Major Nadtochii said in an interview. “We understand that they are working them over, and not in the nicest way.”
Since the explosion, Major Nadtochii said, he had been scrambling to gathering information about the condition of his troops, but remained largely in the dark. The few soldiers he had been able to contact at Olenivka, who were in another location the night of the explosion, described only hearing two bangs. He confirmed that the lists of dead and wounded provided by the Russian government consisted primarily of Azov troops, though he suspected Russian authorities were hiding the true scope of the carnage.
“Honestly nothing surprises me in this war anymore, but somewhere deep in my soul there was hope that nevertheless they were human and might adhere to agreements and rules for conducting war,” he said. “But I’ve become convinced that these are not people, they’re animals.”
The Azov Regiment has become central to the Kremlin’s war narrative. Though now incorporated into the Ukrainian armed forces, its origins as a strongly nationalist volunteer paramilitary group with ties to right-wing fringe figures has been used by the Kremlin to falsely paint all of Ukraine as fascist and to claim that Russia is engaged in “denazification.”
On Tuesday, Russia’s Supreme Court declared the Azov Regiment a terrorist organization, raising fears in Ukraine that Russian prosecutors could eventually charge captive Azov soldiers with grave crimes and block their return to Ukraine in prisoner swaps.
In response to the designation, Ukraine’s National Guard issued a statement reaffirming the Azov Regiment’s place within the chain of command of the Ukrainian armed forces.
“Following the horrible execution of prisoners of war in Olenivka,” the statement said, “Russia is searching for new excuses and justifications for its war crimes.”
Michael Schwirtz and Stanislav Kozliuk from reported from Odesa, Ukraine, Christiaan Triebert from New York and Kamila Hrabchuk from Kyiv, Ukraine.
