Ukraine on Saturday pressed Russia to provide proof that a military plane shot down earlier in the week had been carrying dozens of Ukrainian prisoners of war, as it claimed.
The latest twist in the bitter row over the incident came as Ukrainian officials said a Russian raid had killed two civilians near their border.
Ukraine's spy chief 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 were killed when Kyiv shot down an Ilyushin-76 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 aircraft.
"There are a number of factors that are unclear," Kyrylo Budanov, chief of Ukraine's GUR military intelligence said in an interview with 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 asked on Saturday.
- 'There is nothing' -
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. In another, a forensics team is sealing up a single body bag.
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," Budanov said Saturday. "There is nothing."
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 flown 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.
He said it was "obvious" Ukrainian forces shot it down and had gone ahead with the attack knowing it could have been carrying their own troops.
Kyiv has not yet outlined its version of events, although Ukraine's President Volodymyr Zelensky has called for an international investigation, and both sides have opened criminal probes.
Russian troops killed two civilians Saturday in a raid on the Ukrainian village of Andriivka, four kilometres (2.5 miles) from the border with Russia's western Kursk region, local officials said.
"This morning, an enemy reconnaissance and sabotage group brutally and cynically shot a brother and sister," the Sumy regional administration said in a statement.
The attack happened inside a five-kilometre buffer zone along the border with Russia -- an area where Kyiv had asked residents to evacuate.
Ukraine's Prosecutor General said the victims were a 54-year-old man and a 68-year-old woman, killed while driving in an SUV.
In the Russian city of Saint Petersburg, Putin renewed his attack on the Kyiv administration, claiming "the regime in Kyiv glorifies Hitler's accomplices, the SS".
He was speaking as he visited a memorial to mark 80 years since the end of the Nazi siege of Leningrad, as Saint Petersburg was then called.
He was accompanied by Belarus's President Alexander Lukashenko.
In Ukraine, three French fighters spoke to AFP to deny Russian claims that they had been killed in a recent strike.
Paris has accused Moscow of spreading disinformation about France's role in Ukraine.
