(CNN) — All 74 people, including dozens of Ukrainian servicemen, on board a Russian military plane were killed Wednesday when it crashed in the Belgorod region near the Ukrainian border, Russian officials said.

The Russian Defense Ministry blamed Ukraine for the downing of the Ilyushin-76 cargo plane inside Russian airspace, 5 to 6 kilometers (about 3 to 3.7 miles) from the village of Yablonovo in the Korocha district. It said Kyiv had used an anti-aircraft missile system to target the aircraft and called it an act of terrorism.

“The plane was destroyed by the Ukrainian Armed Forces from the area of Liptsy, Kharkiv region, using an anti-aircraft missile system,” the ministry said in a statement. “The radar equipment of the Russian Aerospace Forces observed the launch of two Ukrainian missiles.”

Kyiv has yet to comment on Moscow’s claim, and CNN cannot independently verify its assertion.

Russian news agencies citing the Defense Ministry said 65 Ukrainian servicemen were on board the plane and being flown to Belgorod ahead of a prisoner swap.

Ukrainian sources claimed the plane was carrying missiles for the S-300 air defense system. CNN cannot independently verify that claim.

A Ukrainian government agency for prisoners of war said it was investigating claims that the plane was carrying Ukrainian servicemen.

A statement from the “Coordination Headquarters for the Treatment of Prisoners of War of Ukraine” provided no further details but did warn Russia was “actively conducting information special operations against Ukraine aimed at destabilizing Ukrainian society.”

Ukraine confirmed that a prisoner of war exchange with Russia had been due to take place on Wednesday. “It is not happening at the moment,” Andriy Yuson, from Ukraine’s Defense Intelligence, told CNN.

Six Russian crew members and three “accompanying personnel” were also on board the plane, Russian officials said. Russian Parliament’s defense committee member Andrey Kartapolov said a second military plane, also an IL-76, was carrying an additional 80 prisoners of war, which was diverted.

Kartapolov said the “Ukrainian leadership was well aware of the impending exchange and was informed of how the prisoners would be delivered. But the IL-76 plane was shot down by three missiles, either with anti-aircraft missile systems or Patriot, or with German-made IRIS.”

Belgorod Governor Vyacheslav Gladkov said the cause of the crash was being investigated. “A transport airplane crashed in the Korochansky district. It went down in a field near a settlement. All those on board died,” Gladkov said. “Now the crash site is cordoned off. All operational services are on site, investigative measures are being carried out,” he added.

“No damage was done to the village, as it [the plane] crashed in a field outside of the village,” a local cleric, Rev. Georgy, rector of the Dimitri Solunsky church in Yablonovo, told TASS.

The Ilyushin Il-76 is a Soviet-era military transport aircraft with a payload of more than 50 tons, according to Europe’s air safety body, Eurocontrol. It has been in service since 1975.

The border city of Belgorod was the site of one of the deadliest Ukrainian attacks on Russian soil late last year. At least 24 people, including three children, were killed and 108 others wounded in the attacks, which sparked retaliatory Russian strikes on the Kharkiv region of Ukraine.

The plane crash comes as Russia’s war in Ukraine is set to enter its third year, with little battlefield progress made by either side in recent months. Western intelligence assessments warn that battlefield movement could further stagnate this year.

Kyiv and Moscow have exchanged prisoners of war throughout the conflict. The largest swap came earlier in January, when the two sides each exchanged over 200 prisoners.

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