DUBAI - Malaysian Prime Minister Najib Razak on Tuesday vowed to bring to justice the perpetrators of the downing of Malaysia Airlines MH17, but said he feared fighting in Ukraine might block access to the crash site.
In an interview with Reuters in Dubai, Datuk Seri Najib also said he hoped to see results over the coming months in the search for missing Malaysian jetliner MH370, bringing closer a solution to the world's greatest aviation mystery.
The plane veered off course and disappeared without a trace earlier this year.
Malaysia has been hit by two unprecedented aviation disasters this year - flight MH370's disappearance in March and the downing of flight MH17 over Ukraine in July.
Mr Najib told Reuters that Malaysia was determined to continue its search for answers for both.
"We want to pursue this (MH17 investigation) until its logical conclusion, which is to bring to justice the people responsible," said Mr Najib, speaking on the sidelines of an Islamic finance conference.
"It's going to be a long, drawn-out process. But we need to do this. We need to show that whoever did it must pay the price. Because you cannot bring down a civilian aircraft... even if you give an excuse that it was unintentional."
MH17 was en route from Amsterdam to Kuala Lumpur with 298 mostly Dutch passengers aboard when, it is widely suspected, a surface-to-air missile shot it down.
Kiev blames separatist rebels in east Ukraine and accuses Moscow of arming them.
The rebels and Moscow deny the accusations.
A report by the Dutch safety board said in September that MH17 crashed after a "large number of high-energy objects" penetrated its fuselage.
Dutch authorities leading the investigation of the crash have come under criticism in the Netherlands from relatives of victims and lawmakers, who say not enough progress has been made in identifying who downed the plane.
Officials say cold weather and continuing hostilities are making progress slow.
"Factions are still fighting each other and there are too many splinter groups, making it very risky for us... we cannot get access to the crash site and that is very frustrating," Mr Najib said.
"I don't think what we're doing is adequate enough."
Local emergency services made a start in October, recovering personal belongings from the crash site, after Mr Najib personally negotiated a deal with the rebels to allow access to the bodies of passengers.
He said the bodies of all but one passenger had been secured now.
Mr Najib said he expects some results in the search for the missing jetliner MH370 after new technology was deployed to scan the ocean bed.
More than two dozen countries have been involved in the air, sea and underwater search for the missing Boeing 777, but months of searches have failed to turn up any trace, even after the search area was narrowed to the southern Indian Ocean.
The next stage of the search began earlier this month when the GO Phoenix search vessel began sonar sweeps of the ocean bed to locate any trace of wreckage.
"We are using the most sophisticated technology now, on Malaysia's expense," Mr Najib said. "So let us hope in the coming months there will be some success. But if you ask me how long it's going to take... no one can give you that answer."
Investigators have said what little evidence they have suggests the plane was deliberately diverted from its scheduled route before plunging in the ocean.
Mr Najib also renewed calls for the international aviation community to come up with tracking systems and other technology to avoid another incident like MH370.
"Capability to track planes should be utilised. With today's technology you can track aircraft in real time and that capability should be utilised.
"You cannot allow somebody on board to switch off the communication systems, including the transponder.
With the current-day technology and tracking systems, we can improve the capability of the black box in terms of its recording, in terms of its length of time, it gives out signals or pings."