A Russian Ilyushin Il-76 military transport plane crashed on Wednesday in Russia's Belgorod region, state news agency RIA quoted the defence ministry as saying.
Video posted on the Telegram messenger app by Baza, a channel linked to Russian security services, showed a large aircraft falling towards the ground and exploding in a vast fireball.
The Il-76 is a military transport aircraft designed to airlift troops, cargo, military equipment and weapons. It has a normal crew of five people, and can carry up to 90 passengers.
Ukrainian military has reportedly said the incident was "their work." It has been reported that 74 people have died in the incident in Korochansky district, northeast of Belgorod city.
Footage on social media showed the moment of the explosion
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Local governor Vyacheslav Gladkov said investigators and emergency workers were already on the scene.
The Kremlin said in response to a reporter's question that it was looking into the situation.
Belgorod region, which borders Ukraine, has come under frequent attack from Ukraine in recent months, including a December missile strike which killed 25 people.
RIA cited the defence ministry as saying that the plane was carrying 65 Ukrainian prisoners of war, alongside six crew members and three other people, when it crashed. The claims have not been verified.
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Footage on social media showed the fireball and a cloud of black smoke in the sky
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The State Duma will prepare an appeal to the United States and Germany in connection with the Il-76 crash, according to chair Vyacheslav Viktorovich Volodin.
Russian MP Popov has said Ukraine was informed about route of Il-76 plane carrying prisoners of war.
Fellow MP Andrey Kartapolov added Russian Il-76 shot down with Ukrainian Patriot or Iris-T missiles in Korochansky District, Belgorod Oblast. These claims have not been verified.
A Russian military blog has reportedly claimed a prisoner exchange was supposedly due to take place in Belgorod Oblast today. This has also not been verified. Details of who was on board has not been verified but Russia and Ukraine regularly swap prisoners of war.
Ukraine's defence ministry and air force did not immediately reply to requests for comment.
Russian presidential spokesperson Peskov said they "will deal" with the incident.
A Russian blog has claimed that residents heard two powerful explosions in air from 30 km away prior to the crash.