Western powers have ratcheted up the pressure on Moscow over the Malaysian plane disaster, as a train loaded with some 280 bodies was finally allowed to leave a rebel-held station four days after the jet crashed in strife-torn east Ukraine.

US President Barack Obama insisted that Moscow force pro-Russian insurgents controlling parts of east Ukraine to cooperate with an international probe into the disaster, and said chaos at the impact site was an “insult” to families of the victims.

The United Nations Security Council has since unanimously adopted an Australia’s draft resolution demanding “full and unrestricted access” for investigators to crash site.

Rebels appear to be co-operating, with Malaysia’s premier saying they had now agreed to give investigators freedom to examine the scene.

A refrigerated train carrying the victims’ remains was heading to the Ukrainian city of Kharkiv where it will be met by senior Australian officials, before being flown to the Netherlands.

• UN pass unanimous resolution condemning downing

Moscow, which has drawn ire for failing to rein in the pro-Russian rebels, meanwhile hit back at US accusations that it supplied the weapons allegedly used to shoot down the airliner.

A senior Russian defence ministry official insisted that “Russia did not give the rebels Buk missile systems or any other kinds of weapons or military hardware”.

Moscow challenged Kiev instead, saying records showed a Ukrainian military plane was flying just three to five kilometres from the Boeing 777 before it crashed on Thursday, killing all 298 people on board.

Ukraine’s President Petro Poroshenko swiftly dismissed that claim, calling it an “irresponsible and false statement” by Russia.

On the ground, the animosity between Ukraine’s warring sides was underlined by intense shelling which erupted in the rebel stronghold of Donetsk.

Five people were killed and 12 wounded, as Ukraine President Petro Poroshenko said he was ordering his troops to hold fire within a 40-kilometre radius around the crash site, where forensic experts were heading.

Meanwhile, the public prosecutor’s office in the Netherlands said it had opened a criminal probe into the downing of the plane, which had 193 Dutch on board.