The UN Security Council has called for "a full, thorough and independent international investigation" of what brought down a Malaysia Airlines plane in eastern Ukraine.
The council approved a statement expressing "deepest sympathies and condolences to the families of the victims, and to the people and governments of all those killed in the crash".
It came as all sides traded accusations as the investigation into the crash gathered pace.
Ukraine has called for an international probe to determine who attacked the plane and insisted it was not its military. Officials accused separatists of shooting down the plane.
The rebels denied it and claimed government forces were behind the crash, which was denied by Ukrainian president Petro Poroshenko.
US intelligence authorities said a surface-to-air missile downed the plane, but have not yet been able to say who fired it.
Security Council members stood in a moment of silent tribute to the 298 victims at the start of an emergency council meeting.
The council called for an investigation "in accordance with international civil aviation guidelines and for appropriate accountability".
It stressed the need for "immediate access by investigators to the crash site to determine the cause of the incident".
Nataliya Bystro, a spokeswoman for Ukraine's emergency services, said rebel militiamen were interfering with the recovery operation.
The crash site is spread out between two villages in eastern Ukraine with pro-Russia separatists apparently controlling access in and out.
Confusion surrounds the fate of the plane's flight recorders after conflicting reports over whether they had been found.
An assistant to the insurgency's military commander, Igor Girkin, said earlier that eight out of the plane's 12 black boxes had been located and Mr Girkin was considering whether to give international crash investigators access to the crash site.
But another separatist leader, Aleksandr Borodai, said later: "No black boxes have been found. We hope that experts will track them down and create a picture of what has happened."
Russian president Vladimir Putin blamed Ukraine for the downing, saying Kiev was responsible for the unrest in its Russian-speaking eastern regions - but did not directly accuse Ukraine of shooting the plane down and did not address the key question of whether Moscow supplied the rebels with such a powerful missile.
Ukraine and the West have accused Russia of supporting the insurgents, a charge Moscow denies.
An angry Australian prime minister Tony Abbott demanded an independent inquiry into the downing, adding: "The initial response of the Russian ambassador was to blame Ukraine for this and I have to say that is deeply, deeply unsatisfactory.
"It's very important that we don't allow Russia to prevent an absolutely comprehensive investigation so that we can find out exactly what happened here.
"This is not an accident, it's a crime."
Australia lost at least 28 people in the disaster.
Ukraine's ambassador to Nato, Ihor Dolhov, said Kiev has evidence from intercepted phone calls proving pro-Russia rebels caused the crash.
But Russian foreign minister Sergey Lavrov dismissed Kiev's accusations that Moscow itself could have been behind the attack.
"Regarding those claims from Kiev that we allegedly did it ourselves: I have not heard a truthful statement from Kiev for months," he told the Rossiya 24 television channel.
Anton Gerashenko, an adviser to Ukraine's interior minister, said on his Facebook page the plane was flying at about 33,000ft when it was hit by a missile from a Buk launcher, which can fire up to an altitude of 72,000ft. He said only that his information was based on "intelligence".
The Interior Ministry later released a video purporting to show a truck carrying the missile launcher they say was used to fire on the plane with two of its four missiles apparently missing.
The ministry said the footage was filmed by a police surveillance squad this morning as the truck was headed to the city of Krasnodon, towards the Russian border.
The area has seen heavy fighting between government troops and pro-Russia separatists, and rebels had bragged about shooting down two Ukrainian military jets in the region just a day earlier.
Ukrainian prime minister Arseniy Yatsenyuk described the downing as an "international crime" whose perpetrators would have to be punished in an international tribunal.
"Yesterday's terrible tragedy will change our lives. The Russians have done it now," he was cited as saying by the Interfax-Ukraine news agency.
Kenneth Quinn of the Flight Safety Foundation said an international coalition of countries should lead the investigation. The US has offered to help.
Malaysian transport minister Liow Tiong Lay insisted that the airline's path was an internationally approved route and denied accusations that Malaysia Airlines was trying to save fuel and money by taking a more direct flight path across Ukraine.
"I want to stress that this route is an approved path that is used by many airlines including 15 Asia-Pacific airlines. We have not been informed that the path cannot be used," he said
Malaysia's prime minister Najib Razak said there was no distress call before the plane went down.
Aviation authorities in several countries, including the FAA in the United States, had issued previous warnings not to fly over parts of Ukraine after Russia annexed the Crimean peninsula in March. Within hours of the crash, several airlines announced they were avoiding parts of Ukrainian airspace.