Early Tuesday, the rebels handed over both black boxes from Flight 17 to Malaysian investigators in Donetsk.
A rebel leader, Alexander Borodai, said the orange-colored flight recorders were being handed over to Malaysian officials on the condition that they would be delivered to experts at the International Civil Aviation Organization.
"I can see that the black box is intact even though a little bit damaged, but in a good condition," said Col. Mohamad Sakri of the Malaysian National Security Council. He added that the number one priority was for the bodies of the victims to be delivered to Amsterdam.
Earlier, a team of international observers at the sprawling crash site described strange behavior by workers.
"When we were leaving, we observed workers there hacking into the fuselage with gas-powered equipment," OSCE spokesman Michael Bociurkiw said.
He said there was no security perimeter Monday at one of the bigger debris fields, and monitors saw that one of the largest pieces of the plane "had somewhat been split or moved apart."
In Washington, Obama asked, "What exactly are they trying to hide?"
"This is an insult to those who have lost loved ones. This is the kind of behavior that has no place in the community of nations," he said.
On Sunday, the US said there was "powerful" evidence that the rebels had shot down the plane with a Russian surface-to-air missile, including video of a rocket launcher, one surface-to-air missile missing, being driven away from the likely launch site; imagery showing the firing; phone calls claiming credit for the missile strike and phone recordings said to reveal a cover-up at the crash site.
The Russian Defense Ministry offered its own evidence on Monday, showing photos it said proved that Ukrainian surface-to-air systems were operating in the area before the crash - nine times alone the day the plane was brought down.
Russian officials also said they had evidence a Ukrainian Su-25 fighter jet had flown "between 3 to 5 kilometers (2 to 3 miles)" from the Malaysia Airlines jet.
"(The plane) is armed with air-to-air R-60 rockets, which can hit a target from a distance of up to 12 kilometers (7 miles) and guaranteed within 5 kilometers (3 miles)," said the chief of Russia's General staff, Lt. Gen. Andrei Kartopolov.
Defense Ministry officials insisted Russia had not given the rebels any surface-to-air missiles - and said they have no evidence that any missiles were launched at all. They asked the US to share any satellite images of the launch.
Putin accused others of exploiting the downing of the plane for "mercenary objectives." He said Kiev authorities had reignited the fighting after a unilateral cease-fire expired without progress on peace talks.
At the UN, the Security Council unanimously adopted a resolution demanding international access to the crash site and an end to military activities around the area, following intense pressure on a reluctant Russia to support the measure.
Fighting in eastern Ukraine began in mid-April after Russia annexed Ukraine's southern Crimean Peninsula a month earlier.
Battles erupted again Monday between the separatists and government troops in Donetsk, according to city authorities. A witness heard several explosions and saw smoke rising from the direction of the city airport.
