MOSCOW â€” Pro-Russian separatist leaders in the eastern Ukrainian region of Luhansk have blocked access to Dutch law enforcement officials pursuing an investigation into the downing of a Malaysian jetliner nearly a year ago, the Netherlands Public Prosecution Office said on Saturday.
The obstruction by separatist officials prompted the investigators, from the Dutch National Police and Ministry of Defense, to cut short their field work in Ukraine without conducting research into cellphone towers and cellular networks in the region, the public prosecution office said.
The passenger jet, Malaysia Airlines Flight 17, was shot down on July 17 as it flew over the war zone in eastern Ukraine during a journey from Amsterdam to Kuala Lumpur, killing all 298 people on board, including 196 Dutch citizens.
Based on preliminary analysis and intelligence, including from the United States government, the aircraft was widely believed to have been destroyed by a surface-to-air missile fired from territory controlled by Russian-backed separatist forces.
The separatist groups, however, strongly deny that they had anything to do with the crash, and the Russian government has sought to provide evidence that the plane was fired upon by a Ukrainian jet fighter.
And on Friday, a senior Russian official said the Kremlin would oppose a plan by Malaysia calling on the United Nations Security Council to create a tribunal to try suspects in the downing of the jetliner. Calling the idea â€œill-timed and counterproductive,â€ Gennady Gatilov, a deputy foreign minister, told Russian news agencies, â€œWe need to wait for the end of the investigation, not adopt hasty resolutions on the creation of tribunals.â€
An official international inquiry into the cause, which is being led by the Dutch aviation safety agency, has not made any official determination.
A preliminary report issued in September found that the aircraft had experienced no technical difficulties and had made no distress call, while wreckage of the plane indicated that it was destroyed after being hit by high-energy projectiles that ripped it apart in midair. Although the report did not say so, that kind of damage is consistent with a missile attack.
The destruction of the plane sharply focused international attention on the worsening violence in Ukraine, and briefly put Russia under intense pressure over its role in the conflict, amid suspicions that it had supplied the missile system.
But as the first anniversary of the disaster approaches, Dutch officials have expressed mounting concern over the lack of progress in determining the precise cause and in identifying those responsible, a likely reflection of intensifying political pressure, including from families of the victims.
The criminal investigation is being carried out separately from the safety investigation. The Dutch officials spent about two weeks in eastern Ukraine, mostly at the crash site in the region of Donetsk, which is also largely controlled by pro-Russian separatist forces. The investigators ended their work on Saturday after concluding they could proceed no further.
In Donetsk, however, investigators received greater cooperation from officials of the self-proclaimed Donetsk Peopleâ€™s Republic, the Dutch prosecution office said in its statement on Saturday.
Investigators were also aided by the Organization for Security and Cooperation in Europe, which is monitoring the conflict zone.
â€œThe most important goals of the mission were in this region,â€ the prosecution office said. â€œGround samples have been taken at various locations and technical research has been conducted to locate cell towers and check the working of the eastern Ukrainian telephone network. The information that has been collected during the mission will be examined and analyzed in the Netherlands.â€
Efforts to conduct a similar inquiry into cellphone towers in Luhansk were stymied, the prosecution office said.
â€œThe mission was also aimed at technical research into cell towers and telephone network in the Luhansk area,â€ the statement added. â€œThis has until now not succeeded, as representatives of the self-proclaimed Luhansk Peopleâ€™s Republic in talks with the O.S.C.E. until now have refused access to the Luhansk area.â€
Cellphone communications could be integral to the investigation because Ukrainian intelligence services said they had intercepted telephone conversations in which separatist commanders discussed the shooting down of a plane â€” apparently believing their forces had just destroyed a Ukrainian military jet.
One Western official with close knowledge of the work in eastern Ukraine said that the investigators were ill-advised in trying to conduct an inquiry amid continued sporadic fighting. â€œI think they were extremely naÃ¯ve to go back there and launch a criminal investigation in one of the most open and dangerous crime scenes in the world,â€ the official said, speaking on the condition of anonymity because of the delicate politics of the inquiry.
This month, the Dutch foreign minister, Bert Koenders, visited Moscow, where he discussed the inquiries with his Russian counterpart, Sergey V. Lavrov.
In a statement after the meeting, he added: â€œItâ€™s our responsibility to pull out all the stops in order to keep the attention of the international community focused on MH17. We owe it to the victims and the next of kin.â€- The New York Times