MH-17 was on a flight from Amsterdam to Kuala Lumpur with 295 people on board when it came down in eastern Ukraine.
The Ukranian President says it was an "act of terrorism" by separatists, but the rebels say they don't have the weapons capable of such an act.
While most of those on the flight were Dutch, it's been confirmed that at least 27 Australians were among the many nationalities aboard.
Australia's Prime Minister says it's a very sad time, made worse by the fact that it may have been a 'crime...not an accident.'
Correspondent: Barbara Miller, Europe correspondent
Speakers: Najib Razak, Malaysia's Prime Minister; Tony Abbott, Australia's Prime Minister; Huib Gorter, senior vice-president of Malaysia Airlines; Petro Poroshenko, Ukrainian president; Alexander Borodai, prime minister of the self-proclaimed People's Republic of Donetsk.
BARBARA MILLER: Chilling images of the crash site in eastern Ukraine suggest no-one can possibly have survived.
Large pieces of debris from a plane appear to be scattered in fields surrounding smouldering wreckage.
Among the passengers it's now been confirmed a substantial number of Australians.
Huib Gorter is a senior vice-president of Malaysia Airlines.
HUIB GORTER: One hundred and fifty-four Dutch passengers were on board the aircraft, 27 Australian passengers, 23 Malaysian, 11 Indonesian, six from the UK, four from Germany, four from Belgium, three from the Philippines and one Canadian.
BARBARA MILLER: Two hundred and eighty passengers and 15 crew members were on board MH17. The nationalities of some passengers are still being checked. All crew members were Malaysian.
The plane came down around 50 kilometres short of the Russian border with Ukraine.
Pro-Russian separatists hold the region and tensions between the rebels and Ukrainian authorities have been escalating in recent days.
Rebels say they shot down two Ukrainian jets this week.
So it wasn't long before the blame game began.
Ukrainian president Petro Poroshenko:
PETRO POROSHENKO (translation): I just finished a conversation with the prime minister of the Netherlands. I offered our condolences on behalf of the Ukrainian people and invited Dutch experts to open an investigation of this act of terrorism. I would like to bring your attention to the fact that we are not calling it an accident or a disaster but an act of terrorism.
BARBARA MILLER: The rebels have denied they had anything to do with loss of MH-17 and have been quick to issue a counter-accusation.
Alexander Borodai is the prime minister of the self-proclaimed People's Republic of Donetsk.
ALEXANDER BORODAI (translation): A passenger aircraft has been shot down indeed. Shot down by Ukrainian air forces. To tell the truth, this is a provocation on purpose.
BARBARA MILLER: The Malaysian prime minister Najib Razak.
NAJIB RAZAK: 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 swiftly be brought to justice.