A Malaysia Airlines plane carrying 283 passengers and 15 crew crashed Thursday in the battle-torn east Ukraine region of Donetsk, where U.S. intelligence agencies say it was struck by a ground-to-air missile.

The U.S. agencies are divided over whether the missile was launched by the Russian military or by pro-Russia separatist rebels, who officials say lack the expertise on their own to bring down a commercial airline in midflight. Ukraine, which also has sophisticated antiaircraft weaponry, said it hadn't shot any such missiles...