International investigators will on Tuesday release their final report into the shooting down of Malaysia Airlines flight MH17 over war-torn Ukraine, but the burning question of who was to blame will remain unresolved.

The Dutch Safety Board (OVV), leading a team of international investigators since the Boeing 777 went down last year, will release the report at 1115 GMT at the Gilze-Rijen air force base in southern Netherlands.

All 298 people on board -- most of them Dutch -- including the 15 crew members died when the routine flight between Amsterdam and Kuala Lumpur was brought down, possibly by a missile, during heavy fighting between Ukrainian forces and pro-Russian separatists.

Tuesday's report -- 15 months after the July 17, 2014 crash -- will focus on four subjects, the Dutch board said in a statement.

"The cause of the crash; the issue of flying over conflict areas; the question why Dutch... relatives of victims had to wait two to four days before receiving confirmation from the Dutch authorities that their loved ones were on board; and lastly, the question as to what extent the occupants of flight MH17 were conscious of the crash."

But as the board has pointed out many times, it will not assign blame nor say who pulled the trigger.

"It is the purpose of the criminal investigation to answer those (questions)," it said.


Blame game


Kiev and the West however have pointed the finger at the separatists, charging they may have used a BUK surface-to-air missile supplied by Russia to blow the plane from the sky.

The Russian maker of the BUK missile said it too will hold a press conference in Moscow on Tuesday to explain the "real reasons" for the disaster after holding an "experiment" that entailed detonating a missile next to a plane.

Fragments of a Russian-made BUK were found at the crash site earlier this year. But Moscow denies involvement and instead has accused Ukraine's military of being behind the tragedy.

The downing of MH17 further strained relations between Russia and the West, already at their lowest ebb since the Cold War due to the conflict in eastern Ukraine.

The United Nations estimates some 8,000 people have been killed and 18,000 others have been wounded since clashes erupted there in April 2014.

The report's release also comes amid heightened concern over Moscow's role in Syria, where it has launched air strikes which it says are aimed at routing jihadists.


'New answers'


Relatives of the victims, who in July marked the first anniversary of the crash with an emotional gathering attended by over 2,000 people, said they believed the final report will at least answer some questions.

They will also for the first time be confronted with the harrowing sight of a partial reconstruction of the doomed plane made from pieces of wreckage brought back from the crash site.

"The report will throw new light onto the case as we know it at the moment," said Dennis Schouten, chairman of the MH17 Air Disaster Foundation.

Relatives understand that the criminal probe has not yet been completed to answer who was behind the probable firing of the missile, he told AFP.

"That must come from the criminal probe and has to be proved properly," said Schouten.

But with the release of Tuesday's report "the net is certainly drawing a little closer," he added.

"Is there more than one guilty party? The airlines and their flight routes? So many questions remain."


Prosecution


Both the Russian and Ukrainian militaries have BUK missiles in their arsenal, and the system's Russian manufacturer said in June that based on publicly available photographs of the wreckage the plane was likely shot down by one of its projectiles.

But Russia in July vetoed a bid at the UN Security Council to set up an international tribunal to try those behind the downing of the aircraft.

Countries involved in that bid are now looking at other means to carry out a prosecution, although no suspects have yet been publicly identified.