An initial review of US intelligence suggests pro-Russian separatists likely shot down a Malaysian airliner over Ukraine, but Washington is still examining the evidence, a US official said Friday.
"There are indications (the separatists downed the plane) but there's no final conclusion," the US official, who spoke on condition of anonymity, told AFP.
Military and intelligence analysts were still poring over satellite and other data and there were still unanswered questions. But a preliminary review suggested the airliner was hit by a SA-11, a common variant of Russian-made Buk surface-to-air missile.
At the UN Security Council, Washington's UN ambassador Samantha Power said the United States believed Flight MH17 was hit by a missile fired from the eastern region held by pro-Russian separatists.
US officials on Thursday had said intelligence analysts concluded that the Boeing 777 airliner -- which had 298 people on board -- was shot out of the sky by a surface-to-air missile.
The plane was flying at about 33,000 feet (10,000 meters) when it went down, putting it well within reach of Russian-made missiles possessed by both Ukrainian and Russian forces.
The Buk surface-to-air missile systems are "fairly sophisticated" and require some training to use, as a radar operator must coordinate with those launching the weapon, the US official said.
"It begs a lot of questions," the official said.
The training needed to employ the missiles raised the possibility that the pro-Moscow separatists may have received help from the Russians, that Russian operatives were on the ground or that Russian troops on the other side of the border launched the missile in error, other officials said.
At the United Nations, Power said it was "unlikely that the separatists could effectively operate the system without assistance from knowledgeable personnel."
"Thus we cannot rule out technical assistance from Russian personnel in operating the systems," she said.
Ukraine's government also had the Buk systems but there was no evidence Kiev had those missiles in the area where the plane was shot down, according to Power.
She also said Ukrainian forces have not fired a single missile at an aircraft during the conflict, despite alleged violations of their airspace.