MH17 Prime Minister Najib Abdul Razak has demanded for "swift justice" if Malaysia Airlines Flight MH17 was shot down in Ukraine.
However, he said Malaysia has yet to confirm Ukraine's claim that Russian-backed separatists shot down the aircraft.
"At this stage, Malaysia is unable to verify the cause of this tragedy. But we must and we will find out precisely what happened to this flight.
"No stone will be left unturned. If it transpires that the plane was indeed shot down, we insist that the perpetrators must be swiftly brought to justice," he told a press conference at Sama-Sama Hotel, Sepang.
During his seven-minute press conference, Najib revealed that he spoke to US President Barack Obama, Ukraine President Petro Poroshenko and Netherlands Prime Minister Mark Rutte.
"I received a call from President Obama. He and I both agreed that the investigation must not be hindered in any way.
"An international team must have full access to the crash site and no one should interfere with the area or move any debris including the black boxes," he said.
Najib said Poroshenko has assured an independent investigation and will negotiate with the rebel forces to establish a "humanitarian corridor" to the crash site in Eastern Ukraine.
He said MAS confirmed that Flight MH17 did not make any distress call when it went down.
"The aircraft flight route was declared safe by the International Civil Aviation Organisation and the International Aviation Transportation Association stated the airspace the aircraft traversed was not subject to restrictions," he added.
'A tragic year for Malaysia'
Najib said the Boeing 777-200 emergency locater beacon is located at 48Ě 07' 23", 38Ě 31' 33", according to Kiev's air traffic control.
According to Google Maps, the coordinate is near the city of Krasnyi Luch in the Luhansk Oblast province in south-eastern Ukraine.
"This is a tragic day in what has already been a tragic year for Malaysia.
"As we work to understand what happened, our thoughts and prayers are with the families and friends of those on board the flight," said the prime minister.
"I cannot imagine what they must be going through at this painful time.
"The flight passengers and crew came from many different countries but today, regardless of nationality, we are all united in grief," he added.
The downing of Flight MH17 comes just slightly more than four months after Flight MH370 went missing.
Najib, who appeared sombre, was flanked by Defence Minister Hishammuddin Hussein, Foreign Affairs Minister Anifah Aman, Minister in the Prime Minister's Department Wee Ka Siong and Deputy Transport Minister Aziz Kaprawi.
N ewly-minted Transport Minister Liow Tiong Lai is on his way back from Beijing and is expected to hold a press conference at 9am.
Najib said Putrajaya is deploying a special disaster team and a medical team to Kiev while MAS is in the process of notifying the families of those on board the aircraft.
Flight MH17 was carrying 280 passengers and 15 crew members and was due to arrive in Kuala Lumpur at 6.10am after taking off at 12.15am from Amsterdam.