The call for witnesses included an emotional video featuring the parents of one of the Australian victims, 29-year-old Victor Oreshkin.

His mother, Vera Oreshkin, called her son a "gift from God."

"This tragedy has blown a hole in my heart and it will never be filled. Ever," she says in the video.

The appeal comes days before the resumption on Monday of the trial of three Russians and a Ukrainian charged with multiple murder for their alleged role in shooting down on July 17, 2014, the Boeing 777 that was flying from Amsterdam to Kuala Lumpur.

Of the 298 who died, 38 were from Australia.

The plane was blown out of the sky over conflict-torn eastern Ukraine, where government forces were battling pro-independence rebels.

None of the suspects has been extradited to the Netherlands to face justice and the trial that started in March 2020 is continuing in their absence. It is expected to continue into next year.

Investigators say the Buk missile and its launcher, known as a Telar, were trucked into Ukraine from the Russian 53rd Anti Aircraft Missile Brigade, which is based in Kursk. Russia has steadfastly denied involvement in downing the plane.

The appeal says that the information now sought is not to bolster the case against the four suspects on trial, but for the investigation into who ordered the missile sent to Ukraine and the crew of the Telar.

Speaking in Russian, Oreshkin says: "The truth must be established and made known to everybody."

Her husband, Serge, holding a framed photograph of their son, adds: "We would like to see somebody take the responsibility for what happened."

Investigators said they are seeking "pictures, videos, relevant email messages or military orders."

In an open letter to the citizens of Kursk, the investigators said: "Our investigation is already at a very advanced stage, but it is not yet complete. We would like to hear from everybody, also from the Russian soldiers, about what really has happened."

Australian Associated Press