Prime Minister Tony Abbott said the loss of 27 Australians was a tragedy and "an unspeakable crime" if it was brought down by a missile.
A global air safety group, the Flight Safety Foundation, says an international coalition of countries should lead the investigation of a Malaysia plane that crashed in Ukraine.
Ukraine's UN ambassador says the Malaysian airliner would not have crashed if Russia hadn't given pro-Russian separatists a sophisticated missile system that can hit planes.
Yuriy Sergeyev told The Associated Press in an interview that Russia bears responsibility for the disaster, along with the separatists, whom he called "terrorists."
Malaysia Airlines says all of its European flights will take routes avoiding Ukraine.
The airline says there were 283 passengers and 15 crew - making a total of 298 people.
The airline says the route had been declared safe by the international civil aviation organisation.
An updated statement from Malaysia Airlines states that 9 Britons died in the crash.
Three infants were also on the plane - 1 from Indonesia and 2 from Malaysia.
41 passengers remain unverified.
It is being reported that 'many' on crashed plane were heading to a Melbourne AIDS conference.
"My thoughts & prayers to families of those tragically lost on flight #MH17. Many passengers were enroute to #AIDS2014 here in #Melbourne," tweeted UNAIDS executive director Michel Sidibe.
Barack Obama has phoned the Netherlands prime minister to say the US would support a "prompt, full, credible and unimpeded international investigation".
Other airlines including Korean, Asiana and Qantas have all said they moved their flight routes over Ukraine months ago.
Australian Prime Minister Tony Abbott has said "Russian-backed rebels" were apparently behind the shooting down of the Malaysia Airlines passenger jet over eastern Ukraine.
The US aviation agency has ordered US aircraft not to fly over eastern Ukraine after the downing of the Malaysian Airlines plane.
Malaysia Airlines shares have fallen more than 10% as a result of the Ukraine crash, AFP has reported.
The airliner downed in Ukraine did not make any distress call, Malaysia's prime minister has said.
The International AIDS Society has expressed its sadness at the news that delegates to its 20th international conference in Melbourne were on board the Malaysian Airlines flight MH17.
The OSCE says Ukrainian separatists will provide safe access and security guarantees to the national investigation commission in the area under their control.
Foreign Minister Julie Bishop confirms the Australian death toll from MH17 is now 28, but says "it could be higher".
Malaysian Airlines stock lost more than 17% of their value at one stage on the country's stock market - down 13% in the first few minutes of trading.