The United States says a surface-to-air missile fired from a rebel-held region in eastern Ukraine took down Flight MH17, as the plane -- carrying 298 people on board -- was travelling from Amsterdam to Kuala Lumpur.
U.S. President Barack Obama said Russia likely bears some responsibility for the crash.
"A group of separatists can't shoot down military transport planes or they claim, fighter jets without sophisticated equipments and sophisticated training. And that is coming from Russia."
But a lack of access to the crash site is complicating investigations.
A delegation of the Organization for Security and Cooperation in Europe had just 75 minutes Friday to examine some 200 meters at the crash scene before being forced to leave by pro-Russian militants.
Pieces of the airplane are spread over several kilometers.
The UN Security Council held an emergency session, calling for a full and independent international investigation into what happened.
They urged that immediate access be given to monitors investigating the case.
Russia denies playing any part in the crash.
Referring to Ukraine's claims that Russia was connected to the missile attack, Foreign Minister Sergey Lavrov told state-run broadcaster Russia 24 that he has not heard Kiev tell the truth for months.
Russian President Vladimir Putin said the crash was a tragedy.
He called for a ceasefire and peace talks in Ukraine, but fresh clashes were reported Friday less than 100 kilometers from the crash site.
Hwang Sung-hee, Arirang News.