Prime Minister Tony Abbott has said it would be an "unspeakable crime" if a Malaysia Airlines passenger plane en route to Kuala Lumpur from Amsterdam was shot down and the perpetrators "should be swiftly brought to justice".
Mr Abbott offered his deepest condolences to the families and friends of the people involved in what was a "terrible tragedy".
"We can assure families that, at the highest levels of government, we feel for them, we grieve with them and we pray for them,'' he said. ''That's the first thing we go. The second thing is to try to provide whatever practical assistance we can, in terms of counsel and the repatriations of remains and so on."
In Moscow, Russian President Vladimir Putin blamed the Ukrainian government for the crash of a Malaysian Airlines jet that was shot down over eastern Ukraine, killing all 295 people on board.
The government in Kiev is responsible for the fighting in eastern Ukraine between government troops and pro-Russian rebel forces which caused the downing of the civilian aircraft, Putin said at a cabinet meeting last night, according to a transcript released by the Kremlin. Putin has repeatedly denied Russian involvement in the fighting in Ukraine.
Mr Putin said Ukraine bore responsibility for the downing of a passenger plane, saying it would not have happened if Kiev had not resumed a military campaign against separatists.
"I want to point out that this tragedy wouldn't have happened if there was peace in this land, or at least if fighting hadn't resumed in the southeast of Ukraine," Putin said. "And undoubtedly, the state on whose territory this happened is responsible for this awful tragedy."
In the United States, President Barack Obama said the nation's top priority was to determine whether American citizens were on board. Obama said the crash "looks like it may be a terrible tragedy" and offered his thoughts and prayers to families of the victims, "wherever they call home".
"The United States will offer any assistance we can to help determine what happened and why," he said in brief comments before delivering a speech at the Port of Wilmington in Delaware.
In Germany, Chancellor Angela Merkel, who has worked closely with Obama on sanctioning Russia for its Ukraine policies, refrained from placing blame, while saying in a statement that if reports the plane was shot down prove true it would be a "tragic escalation" in the conflict.
In the Ukraine, the office of President Petro Poroshenko mentioned the possibility that the plane had been attacked, claiming that pro-Russia rebels have shot down a number of aircraft in recent days over the territory they claim to control. The office expressed confidence "that those responsible for this tragedy will be brought to justice".
