Ukraine's spy chief on Saturday questioned why Russia had not shown any images of the bodies of Ukrainian soldiers that Moscow claims were killed when a military plane was shot down.
Russia said 65 Ukrainian prisoners of war died when Kyiv shot down a military transport plane on Wednesday near the border between the two countries.
While Kyiv has not outright denied Russia's claims, it has questioned key parts of its narrative -- in particular, who was on board the plane.
"There are a number of factors that are unclear," Kyrylo Budanov, chief of Ukraine's GUR military intelligence unit said in an interview with Ukrainian state TV.
"First of all, they did not show fields covered with corpses and remains," he said.
"If it happened as Russia claims, why does Russia ... continue to hide the bodies?," Budanov said on Saturday.
Russia's Investigative Committee has published three videos of what it says is the crash site.
One showed a blurred close-up of a dead body. Another showed a forensics team sealing up a single body bag. And a third was grainy footage purporting to show vehicles transporting the prisoners to the plane before it took off, but the quality was too poor to verify this.
"There are no corpses. There is nothing," Budanov said Saturday.
Kyiv has confirmed a prisoner exchange was due to take place on the same day and has not explicitly denied shooting down the plane.
But it said Moscow did not request a temporary aerial ceasefire near the border, as it had previously when POWs were being transferred via plane to a scheduled exchange.
Russian President Vladimir Putin said Friday that Budanov's GUR was aware the prisoners were going to be transferred by plane.
Putin said it was "obvious" Ukrainian forces shot it down and that they had gone ahead with the attack knowing it could have been carrying their own troops.
Kyiv has not yet outlined its version of events.
Ukraine's President Volodymyr Zelensky has called for an international investigation.
Both sides have opened criminal probes.
