Obama on Ukraine's Pro-Russia Separatists: 'What Are They Trying to Hide?'

"We have to make sure that the truth is out," the president said.

Armed pro-Russia separatists stand guard at the train station on July 21, 2014 as intense shelling rocked the area, in the rebel stronghold of Donetsk in eastern Ukraine. (National Journal)

Echoing frustrations felt across the world, President Obama called for "immediate and full access to the crash site" of Malaysian Airlines flight 17 from the White House Monday. "We have to make sure that the truth is out," he said.

Obama: "The burden [is] now on Russia to insist that the separatists stop tampering with the evidence."

Four days after the crash, the bodies of victims have not left the country. According to the Associated Press, pro-Russian rebels in Ukraine have seized MH 17's black boxes, and remain in control of the recovered bodies from the crash. The fear is that the pro-Russian rebels have tampered with the evidence. For now, the bodies remain in refrigerated freight cars, and "will go nowhere until experts arrive,'' Donetsk rebel leader Alexander Borodai assured the AP. On Monday, Dutch forensics experts were granted access to the crash site. (Update 12:09 pm: According to reports, the train has left the area, though its destination has yet to be confirmed. According to Reuters, the plane's black boxes will be handed over to Malaysian authorities later Monday.)

"The Russian backed separatists who control the area continue to block the investigation," Obama said. "They've repeatedly prevented international investigators from gaining full access to the wreckage. As investigators approached, they fired their weapons into the air. The separatists are removing evidence from the crash site. All of which begs the question: What are they trying to hide?"

Obama joined in the growing chorus of world leaders demanding greater accountability in the investigation.

"This is still an absolutely shambolic situation," Australian Prime Minister Tony Abbott said Monday. "It does look more like a garden clean-up than a forensic investigation." According to USA Todaythe Dutch investigators have been promised the train would move from the area, but still do not know a time frame. What's worse is that, according to AP reporters, the train's refrigeration systems suffered a power outage overnight.

Obama had direct words for Vladimir Putin on Monday:

President Putin says that he supports a full and fair investigation. And I appreciate those words, but they have to be supported by actions. The burden [is] now on Russia to insist that the separatists stop tampering with the evidence, grant investigators who are already on the ground immediate, full, and unimpeded access to the crash site.

"Over the last several days, our hearts have been absolutely broken as we've learned more about the extraordinary and beautiful lives that were lost," Obama said. "Our immediate focus is on recovering those who were lost."

The United States is ratcheting up pressure on Russia over the Malaysia Airlines crash, which was downed in eastern Ukraine near the Russian border last Thursday. On Sunday, Secretary of State John Kerry called the fight over the crash site "a fundamental moment of truth for Russia" and said that U.S. intelligence "knows to a certainty" that a "major convoy" including tanks and artillery crossed from Russia to pro-Russian separatists in the last month. "What we have is a lot of evidence that points in the direction that raises very, very serious questions," Kerry said on CBS' Face the Nation.

The White House, meanwhile, is hoping that Europe will step up its pressure on Russia. And there are early signs that Europe may take action.

European leaders, too, are intensifying their language against Russian actions. According to the BBC, UK Prime Minister David Cameron, French president Francois Hollande, and German Chancellor Angela Merkel have spoken and "agreed that the EU must reconsider its approach to Russia and that foreign ministers should be ready to impose further sanctions on Russia when they meet on Tuesday," as a Downing Street readout of the call states.

Cameron has also said he hasn't ruled out freezing assets of influential Russians, including members of the Russian parliament. "They have acted to vote again and again to accept this illegal referendum to annex the Crimea to Russia," Cameron said at a Monday press conference. "They are part of the problem, they are part of the cause of this so they should be targeted."