A Russian military transport plane crashed on Wednesday in Belgorod region, close to the Ukrainian border.
Russia’s Defence Ministry has claimed the Ilyushin-76 transport plane was carrying dozens of Ukrainian prisoners of war to be handed over as part of an exchange, and that 74 people were killed in the crash.
But Kyiv said it is still clarifying what happened and warned against sharing “unverified information”.
A video posted on the Telegram messenger app by Baza, a channel linked to Russian security services, appeared to show a large aircraft falling towards the ground and exploding.
“On board were 65 captured Ukrainian army servicemen being transported to the Belgorod region for exchange, six crew members and three escorts,” the Defence Ministry was quoted as saying by the state-run RIA Novosti news agency.
There were no survivors, the region's governor Vyacheslav Gladkov said.
Retired general Andrei Kartapolov, now a Russian MP, claimed the plane had been shot down by three missiles supplied to Ukraine by the West.
He did not reveal the source of the information, and said investigations would reveal whether the missiles were Patriots or IRIS-Ts.
“They shot their own soldiers out of the air. Their own,” he told a plenary session of the Russian Parliament. “Our pilots, who were carrying out a humanitarian mission, were shot down.”
Shortly before the crash, Mr Gladkov said on his Telegram channel a “missile alert” had been set off in the region, and warned residents to take shelter.
Ukraine’s Co-ordination Headquarters for the Treatment of Prisoners of War said it was looking into the crash but did not immediately provide any information and cautioned against sharing “unverified information”.
Russian authorities said a special military commission has been sent to the crash site to investigate.
The Il-76 is designed to transport troops, cargo, military equipment and weapons. It can carry up to 90 passengers.
Russian Foreign Minister Sergey Lavrov, who is in New York for high-level meetings at the UN, told reporters on Wednesday that officials were still “trying to find out the facts”.
He did, however, describe the incident as a “terrorist attack” and demanded the Security Council hold an emergency meeting on the issue.
“Right away, after the aircraft was downed … the Ukrainian side mentioned yet again the victory of their armed forces, but when it became known that it was a POW [prisoners of war] swap plane … the Ukrainian propagandists tried to sweep it under the carpet,” Mr Lavrov claimed.
The Belgorod region has come under frequent attack in recent months, which Russia has blamed on Ukraine, including a missile strike that killed 25 people in December.
Earlier on Wednesday, Ukrainian President Volodymyr Zelenskyy said a Russian missile attack devised to overwhelm Ukraine’s air defences had killed 18 people and wounded 130.
The barrage employing more than 40 ballistic, cruise, anti-aircraft and guided missiles hit 130 residential buildings in three Ukrainian cities, “all ordinary houses”, on Tuesday, Mr Zelenskyy said in a post on social media.
Russia’s attack, which hit targets in Kyiv and Kharkiv, Ukraine's two largest cities, was the heaviest in weeks.
“This year, the main priority is to strengthen air defence to protect our cities and towns, as well as defend frontline positions,” Mr Zelenskyy said.
With the 1,500km front line largely static amid icy weather and as both sides seek to replenish their stockpile of weapons, long-range strikes have become a feature of the war.
Western analysts say Russia has stockpiled missiles to pursue a winter campaign, while Ukraine has sought to strike inside Russia with new types of drone.
Adla Massoud contributed to this report from the UN
