The Boeing 777 crashed Thursday near the city of Donetsk, where pro-Russian separatists have been battling Ukrainian armed forces.
Witnesses who spoke with RIA Novosti reported seeing several dozen bodies and plane debris across a square kilometer area.
MH17 disappeared over Ukrainian airspace while en route from Amsterdam to Kuala Lumpur, with 280 passengers and 15 crew members aboard.
The cause of the crash is under investigation.
The U.S. Department of State said Thursday that it does not yet know whether American citizens were aboard MH17.
On reports of tragic Malaysian plane crash: at this time US do not have any confirmation of cause, individuals on plane or any addl details— Jen Psaki (@statedeptspox) July 17, 2014
Amid suspicion that the plane may have been shot down, U.S. President Barack Obama said Thursday, "The United States will offer any assistance we can to help determine what happened, and why."
Obama spoke by phone with Russian President Vladimir Putin earlier in the day as news of the crash was breaking, and Vice President Joe Biden telephoned Ukrainian President Petro Poroshenko to offer America's help with the crash investigation.