Malaysia on Saturday said vital evidence at the Ukrainian site where flight MH17 went down had been tampered with, calling it a "betrayal" of the lives lost in the disaster.
"The integrity of the site has been compromised, and there are indications that vital evidence has not been preserved in place. Interfering with the scene of the crash risks undermining the investigation itself," said Malaysian Transport Minister Liow Tiong Lai.
"Any actions that prevent us from learning the truth about what happened to MH17 cannot be tolerated. Failure to stop such interference would be a betrayal of the lives that were lost," he told a press conference.
Watch video: Integrity of the plane crash site has been compromised, says Malaysian transport minister
Concerns are mounting over the integrity of the crash zone in rebel-held eastern Ukraine, with the government in Kiev on Saturday accusing Moscow of helping pro-Russian separatist insurgents destroy evidence.
Liow said a Malaysian team, including two air accident investigators who arrived in Kiev early Saturday, were so far unable to access the crash site.
"We must have full access to the site and must ensure evidence on the site is not tampered. We also hope that we can ensure that justice can prevail," he said, adding that he would fly to Kiev later Saturday to expedite matters.
World leaders have called for unfettered access to the crash site to allow for a full investigation into Thursday's apparent shooting down of the jet, that killed all 298 people on board the flight from Amsterdam to Kuala Lumpur.
Ukraine has accused the rebels of shooting down the plane in a "terrorist act" but the separatists allege that Kiev's forces were responsible and Russia's defence ministry says it has evidence that Ukrainian missile systems were active in the area.
"What is most important now, is to ascertain who shot the Malaysian aircraft MH17. We want and demand justice," Liow said.