The Malaysia Airlines aircraft -- a Boeing 777 -- was flying from Amsterdam to Kuala Lumpur when it fell near the city of Donetsk -- a restive area close to the Russian border which has become a stronghold for pro-Russian rebels.
Ukraine's interior ministry adviser says the plane, which was flying at 33-thousand feet, was brought down by a ground-to-air missile.
Both the Ukrainian government and pro-Russian separatist rebels immediately blamed each other for the crash.
"We do not exclude the possibility that this plane was also shot down and stress that Ukrainian Armed Forces did not perform any actions to fire at targets in the air."
Russian President Vladimir Putin is blaming the Ukrainian government for the crash, saying that Kiev bears some responsibility for the fighting that may have led to the jet's apparent downing by missile.
The U.S. government says it'll offer any assistance necessary to Ukraine to determine the cause of the crash.
"I offered President Poroshenko the help of our expertise, our NTSB and other experts in the community. He accepted that help and they will be on their way rapidly to see if we can get to the bottom of this."
More than half of those onboard were Dutch nationals.
There were also 27 Australians, 23 Malaysians, 11 Indonesians and various other nationalities.
More than 40 remain unverified.
Korea's foreign ministry says it's unlikely any Korean passengers were on the plane.
Other airlines have announced they are now diverting flights around eastern Ukraine.
Kim Hyun-bin, Arirang News.
And the UN Security Council is set to hold an emergency meeting in about seven hours to discuss Thursday's downing of the Malaysian airliner.
Earlier, UN Secretary-General Ban Ki-moon called for "a full and transparent international investigation" into the crash.