Ukrainian officials say Russia has provided no credible evidence to back its claims Kyiv forces shot down a military plane carrying Ukrainian prisoners of war (PoWs).
A Russian Ilyushin Il-76 military transport plane crashed in Russia's Belgorod region killing all 74 people on board, Moscow has claimed.
The Russian Ministry of Defence said the plane was carrying 65 captured Ukrainian military personnel, a claim a Ukraine official disputed, when it crashed around 11am local time (8am in the UK) on Wednesday.
On Friday, the Ukrainian agency that deals with prisoner exchanges said Russian officials had, "with great delay", provided it with a list of the 65 Ukrainians who Moscow said had died in Wednesday's plane crash in Russia's Belgorod region.
Ukraine's Co-ordination Staff for the Treatment of Prisoners of War said relatives of the named PoWs were unable to identify their loved ones in crash site photos provided by Russian authorities.
The agency's update cited Ukraine's military intelligence chief, Kyrylo Budanov, as saying Kyiv had no verifiable information about who was on the plane.
On Wednesday, the Russian Defence Ministry said missiles fired from across the border brought down the transport plane that it said was taking the PoWs back to Ukraine.
Local authorities in Belgorod, which borders Ukraine, said the crash killed all 74 people on board, including six crew members and three Russian servicemen.
Mr Budanov, who heads Ukraine's POW agency, said: "We currently don't have evidence that there could have been that many people onboard the aircraft.
"Russian propaganda's claim that the IL-76 aircraft was transporting 65 Ukrainian PoWs [heading] for a prisoner swap continues to raise a lot of questions."
Social media users in the Belgorod region posted videos that showed a plane falling from the sky in a snowy, rural area and a huge ball of fire erupting where it allegedly hit the ground.
Kyiv has neither confirmed nor denied that its forces downed a Russian military transport plane that day, and Russia's claim the crash killed Ukrainian PoWs could not be independently verified.
Earlier on Friday, Mykola Oleshchuk, Ukraine's air force commander, described Moscow's assertion as "rampant Russian propaganda".
Ukrainian officials earlier this week confirmed a prisoner swap was due to happen on Wednesday, but said it was called off.
They said Moscow did not ask for any specific stretch of airspace to be kept safe for a certain length of time, as it has for past prisoner exchanges.
An International Committee of the Red Cross spokesperson in Ukraine urged Russia to return the bodies of any PoWs who might have died in the plane crash.
In an interview with the US-funded Radio Free Europe/Radio Liberty, Red Cross Media Relations Officer Oleksandr Vlasenko also remarked that "very little time" had passed between the initial reports of the incident and Moscow declaring it was ready to return the bodies of the Ukrainian PoWs.
While Ukraine and Russia regularly exchange the bodies of dead soldiers, each trade has required considerable preparation, Mr Vlasenko said.
Ukrainian President Volodymyr Zelensky has called for an international investigation into the crash.
Russia has sole access to the crash site.
Russian President Vladimir Putin has pledged to make the findings of Moscow's crash investigation public.
In his first public remarks on the incident, Mr Putin repeated previous comments by Russian officials that "everything was planned" for a prisoner exchange that day when the aircraft went down.
"Knowing [the PoWs were aboard], they attacked this plane. I don't know whether they did it on purpose or by mistake, through thoughtlessness," Mr Putin said of Ukraine at a meeting with students in St Petersburg.
He offered no details to support the allegation that Kyiv was to blame but said the plane's flight recorders had been found.
"There are black boxes, everything will now be collected and shown," Mr Putin said.