US ambassador to the United Nations Samantha Power has told the UN Security Council that Malaysia Airlines flight MH17 was "likely" brought down by an SA-11 surface-to-air missile.
The Boeing 777-200ER was destroyed as it crossed eastern Ukraine while en route to Kuala Lumpur on 17 July.
Power said that there was "nothing threatening or provocative" about the flight, adding that it was transmitting its assigned transponder code and corresponding with its flight plan.
She added that the Russian-built SA-11 was one of only a small number of missile systems in the region capable of hitting a commercial aircraft at cruise altitude.
Under-secretary general for political affairs Jeffrey Feltman said that, while the UN had "no independent verification" of the cause of the crash, there was "credible" evidence of an "apparent deliberate downing" of a civil aircraft.
Feltman said there was a need for a "full and transparent" investigation and that the UN's ICAO division had offered its investigative capacity to put together an international team.
UK ambassador Mark Lyall Grant said the loss of MH17 was a "dark moment for the international community" and that the violence in Ukraine had reached "monstrous proportions".
Access to the crash site is an "immediate priority", he added, and international representatives should be "unhindered" in their work. There must be "no interference of tampering" with evidence, he said.