International investigators from the MH17 Joint Investigation Team (JIT) accused four pro-Russian military officers of being involved in a missile attack that shot down flight MH17.

The JIT named Russian nationals Igor Girkin, Sergey Dubinskiy, and Oleg Pulatov, and Ukrainian national Leonid Kharchenko as the suspects in the July 2014 attack.

All four worked for the military intelligence agency of the separatist Donetsk People's Republic at the time of the attack.

It is the first time that anybody has been formally named over the attack, almost five years after it happened.

The JIT has long suspected the Russian military of carrying out the attack. Moscow has long denied its involvement.

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International investigators from the MH17 Joint Investigation Team (JIT) have accused four pro-Russian military intelligence officers of being involved in a missile attack that shot down the MH17.

Igor Girkin, Sergey Dubinskiy, Oleg Pulatov, and Leonid Kharchenko all worked for the military intelligence agency (GRU) of the separatist Donetsk People's Republic at the time of the attack, investigators said.

The Donetsk People's Republic GRU is not formally linked to Russia's similarly-named GRU. The Donetsk Republic is a breakaway area of Ukraine which is sustained politically and militarily by Russia.

Girkin, Dubinskiy, and Pulatov are Russian nationals, and all previously worked for the Russia's GRU, the JIT said. Kharchenko is Ukrainian.

The MH17 Joint Investigation Team displayed the photos and names of the four suspects at a press conference on Wednesday. Dutch national police/YouTube

The JIT plans to try the suspects in a criminal court in The Hague beginning March 9, 2020.

In order for the men to be tried in person, they would need to have been successfully apprehended by that date, which may prove difficult. The JIT said the men's named will be added to watch lists around the world.

The investigators said they will ask the Russian and Ukrainian governments to cooperate with their probe.

Malaysia Airlines Flight MH17 crashed in a field in war-torn eastern Ukraine on July 17, 2014, after being hit by a Russian-made Buk missile.

The plane, a Boeing 777 flying from Amsterdam to Kuala Lumpur, went down with 298 people on board. There were no survivors.

The crash site was outside the city of Donetsk, which was held by Russian-backed rebels fighting to break away from the state of Ukraine.

Ukrainian emergency workers carry a body bag near the village of Hrabove, eastern Ukraine, in July 2014. Evgeniy Maloletka/AP

Earlier on Wednesday, open-source investigators at for the website Bellingcat also published a report naming 12 Russian and Ukrainian nationals who they said "had a role in organizing or facilitating the transport of the Buk missile launcher" that shot down MH17.

Girkin, Dubinskiy, Pulatov, and Kharchenko are part of the 12 people named. Bellingcat said it identified them through intercepted phone conversations discussing the Buk missile.

The JIT has long suspected Russian-backed separatists of carrying out the attack.

In a preliminary report published last May, the investigators said the missile came from the Russian military's 53rd antiaircraft missile brigade based in Kursk, a city near the Russia-Ukraine border.

They cited distinctive identifying marks on recovered missile fragments in support of their conclusion.

Read more: Investigators have for the first time directly linked the Russian military to the attack on Flight MH17

Missile fragments from the Buk missile that downed MH17. Dutch National Police/YouTube

The JIT on Wednesday also showed footage of a Buk missile transporter going from Russia to Ukraine before the attack, and back to Russia after the attack.

The MH17 Joint Investigation Team showed footage of a Buk missile transporter moving equipment from eastern Ukraine to Russia after the missile attack on MH17 in July 2014. Dutch national police/YouTube

Russia has repeatedly denied its involvement in the attack.

The country's defense ministry said last September it had evidence the missile was actually fired by Ukrainian forces, and that the joint investigative report in May was "factually inaccurate on several points."