A resolution demanding unrestricted access to the Malaysia Airlines crash site and a full international inquiry into the shooting down of flight MH17 has been approved unanimously by the United Nations Security Council.
Under intense diplomatic pressure over its support for Ukrainian separatists blamed by the West for the deaths of the 298 passengers and crew, Russia gave its support to the Australia-led call.
The UK's ambassador to the UN Mark Lyall Grant said the resolution spelled out the world's demands for an end to the "inexcusable" treatment of the victims' by insurgents controlling the area whose behaviour had been "sickening and appalling beyond belief".
"We owe it to the memory of those 298 victims to ensure that their remains are treated with dignity and with respect. And we owe it to them to find out exactly what happened on the afternoon of July 17," he told an emergency session in New York.
"That is the purpose of Resolution 2166. It is a united demand by the whole international community for the dignified, respectful and professional treatment and recovery of the victims."
He went on: "The site must be preserved and investigators must immediately be granted safe, secure, full and unrestricted access".
In a direct message to the Russians, Mr Lyall Grant also said the events " should serve as a wake-up call in Moscow and prompt a profound re-examination of Russia's policy of supporting, training and arming armed separatists in Eastern Ukraine".
The vote came after Malaysia's prime minister announced that separatist leaders had agreed to hand over the bodies of victims of the Malaysia Airlines crash, along with the plane's black boxes, and to allow international investigators access to the site.
Najib Razak said he had secured agreement from Alexander Borodai, the self-proclaimed prime minister of the "Donetsk People's Republic", after days of behind-the-scenes efforts to establish contact with those in control of the crash site.
David Cameron called on Russian president Vladimir Putin to end his support for separatists and warned Moscow it faced international isolation, including a "new range of hard-hitting economic sanctions" from the EU.
In a statement to the House of Commons, Mr Cameron said Russia was facing a "defining moment" and warned that Europe would fundamentally change its relations with its giant eastern neighbour if Mr Putin continued to foment violence and instability in Ukraine.
Foreign Secretary Philip Hammond will tomorrow meet EU counterparts in Brussels at a meeting in which the UK hopes to accelerate the implementation of extended sanctions on specific Russian businesses, organisations and individuals, as well as discussing broader sanctions which could target wider sectors of the Russian economy, such as financial services, energy exports, trade and defence co-operation.
In a statement, Mr Razak said he had spoken personally to Mr Borodai and agreed that the remains of 282 victims of the crash, accompanied by six Malaysian members of the recovery team, will be moved by train this evening from Torez to the city of Kharkiv, where they will be handed over to Dutch officials.
The remains will be flown to Amsterdam on a Dutch C130 Hercules, together with the Malaysian team.
The black boxes were due to be handed over to a Malaysian team in Donetsk this evening, said Mr Razak.
Independent international investigators will be guaranteed "safe access to the crash site to begin a full investigation of the incident", he said.
Mr Cameron told MPs: "The world is watching. President Putin faces a clear choice in how he decides to respond to this appalling tragedy. I hope he will use this moment to find a path out of this festering and dangerous crisis by ending Russia's support for the separatists.
"If he does not change his approach to Ukraine in this then Europe and the West must fundamentally change our approach to Russia."
Following phone calls in recent days with European leaders including German chancellor Angela Merkel and French president Francois Hollande, Mr Cameron said that for too long there had been "reluctance" on the part of some European nations to face up to the implications of the unrest in eastern Ukraine.
"If Russia does not change course then we must be clear Europe must keep increasing the pressure: Russia cannot expect to continue enjoying access to European markets, European capital, European knowledge and technical expertise while she fuels conflict in one of Europe's neighbours," the PM told MPs.
"We must do what is necessary to stand up to Russia and put an end to the conflict in Ukraine before any more innocent lives are lost."
Mr Cameron, who also discussed the Ukraine crisis at a meeting of the National Security Council, dismissed Mr Putin's "bluster and obfuscation" over the crash and rejected claims that Ukraine's armed forces could have fired the surface-to-air missile that downed the Malaysian jet at 33,000ft.
"The picture is becoming clearer and the weight of the evidence is pointing in one direction: MH17 was shot down by an SA-11 missile fired by separatists," he said.
French arms sales and German dependence on Russian fossil fuels have been seen as possible barriers to tougher measures, but Britain will argue in Brussels that the whole union must share the burden.
Mr Putin warned Western powers not to use the incident to advance "vested interests" at Russia's expense.
The resolution stresses the need for a "f ull, thorough and independent international investigation into the incident in accordance with international civil aviation guidelines" and calls on all states to " provide any requested assistance to civil and criminal investigations".
It calls on groups in the area to "refrain from any actions that may compromise the integrity of the crash site" such as "destroying, moving, or disturbing wreckage, equipment, debris, personal belongings or remains".
Demanding a ceasefire in the immediate area, it says there must be "safe, secure, full and unrestricted access to the site and surrounding area for the appropriate investigating authorities" and a " dignified, respectful and professional treatment and recovery of the bodies of the victims" immediately.
Those responsible must be held to account, it goes on, and " all states cooperate fully with efforts to establish accountability".
Australian foreign minister Julie Bishop, whose country lost 37 citizens and residents in the crash, addressed the meeting, calling the resolution an "unambiguous response from the international community to an utterly deplorable act".
The "grotesque violations at the crash site" demanded such a response, she said.
Mr Hammond told a meeting of the National Security Council that a train carrying the bodies was on its way to Kharkiv, where one of a team of UK experts will be on hand to assist with the identification process.
Others will travel to the Netherlands to help with the repatriation of the victims.
The NSC " agreed that the UK should work with our European partners and the US to ensure that we do what is necessary to stand up to Russia and to make clear that they must take steps to put an end to the conflict in Ukraine", a Number 10 spokeswoman said.
"The first step should be further EU sanctions at the Foreign Affairs Council tomorrow with a view to ratcheting up the pressure further on Russia in the future if President Putin does not change course.
"The NSC concluded that the European Union also needed to have a broader review of its long term relationship with Russia given her behaviour over recent months."