The Ukrainian prisoners of war killed last week in an explosion at their barracks were the victims of a Kremlin special operation plotted in advance and approved at the highest levels, senior government officials in Kyiv have claimed. Citing intelligence, satellite data and phone intercepts, the officials said the inmates were killed in a callous and premeditated war crime. They suggested it was carried out by Russian mercenaries from the Wagner Group, working closely with Vladimir Putin’s FSB spy agency. The dead Ukrainians were members of the Azov battalion, who defended the Azovstal steel plant in Mariupol until their capture in May. They were being held at a prison in Olenivka, close to the frontline and about 10 miles south of occupied Donetsk. An adviser to Ukraine’s president, Volodymyr Zelenskiy, said multiple clues pointed to Moscow’s guilt. They said graves were dug next to the barracks shortly before the attack, and a Russian information campaign was launched describing the fighters as terrorists. The prisoners were moved to the building the day before Friday’s explosion. The Russians rebased their artillery near the prison complex in an unsuccessful attempt to draw return Ukrainian fire. “This was a provocation and mass killing by the Russian side. It was organised by Putin’s regime,” claimed the official, who declined to be named. Putin may have personally authorised the attack, they speculated, adding: “Russia is not a democratic state. The dictator is personally responsible for everything, whether it’s the shooting down of MH17, Bucha or Olenivka. For some time we have not seen Mr Putin. When is he going to recognise the atrocities he has committed?” Russia’s defence ministry says Ukrainians destroyed the building using a Himars long-range missile made and supplied by the US. Footage broadcast on Russian television on Friday showed charred bodies, dismembered limbs and tangled metal from bunkbeds, as well as a hole in the prison’s roof. Advertisement The Biden administration says there are no indications that Ukraine attacked the site. Satellite photos released by Maxar Technologies reveal that surrounding buildings were wholly undamaged. Russian guards escaped without injury. The Institute for the Study of War, a US-based thinktank, said the evidence strongly suggested Russia caused the blast, using either a “precision strike or an internally planted incendiary or explosive”. It said there were no shell craters in the vicinity. The Kyiv official said the Russian Himars claim was “stupid” and made no sense, pointing out that the Azov fighters were regarded by Ukrainians as national heroes. “This was a terrorist act approved at the highest level. It wasn’t a tactical decision,” they said. Zelenskiy has called for an independent investigation into what happened. So far the Kremlin has refused to give access to the site to the Red Cross and UN, which helped negotiate the surrender of the Azovstal defenders and secured guarantees from Moscow that they would be properly treated. Ukraine has not been able to confirm the number of casualties, put by the Russian defence ministry at 53 dead and 75 injured. Names remain confidential. Officials in Kyiv were unable to say on Wednesday where the apparent survivors were now being kept. In other developments in the Ukraine war: Germany’s chancellor, Olaf Scholz, has said Russia has no reason to hold up the return of a gas turbine for the Nord Stream 1 gas pipeline. “The turbine works,” he said. It has been stranded in Germany after servicing in Canada, in a standoff that has led to gas flows to Europe plunging to 20% of capacity. The first shipment of more than 26,000 tons of Ukrainian food was cleared to proceed towards its final destination in Lebanon, the UN said. The Razoni left Odesa on Monday under a Black Sea deal agreed by Kyiv and Moscow and brokered by the UN. So far the deal appears to be holding. More than 10m border crossings in and out of Ukraine have taken place since Russia’s invasion on 24 February. Nearly 6.2 million refugees are now living across Europe, the UNHCR said, with the biggest number, 1.25 million, based in neighbouring Poland.