GRABOVE, Ukraine (CNN) -- Pro-Russian rebels at the crash site of Malaysia Airlines Flight 17 have granted European monitors and experts nearly "unfettered access" to wreckage Monday, according to a spokesman for Security and Co-operation in Europe.
The rebels even provided some perimeter security to keep journalists at bay, creating a "dome of tranquility" for the OSCE monitors, three Dutch forensic experts and a handful of Ukranian aviation experts now at the scene, Michael Bociurkiw said Monday in a briefing hosted by the Ukrainian Crisis Media Center.
His assessment follows a trend of improving access for monitors at the site, which is in the middle of territory held by rebels fighting Ukraine's central government.
However, it remains difficult to get to the site, and Bociurkiw had no information about the status of a team of international crash experts staging in Kharkiv to inspect the debris.
Earlier, the Ukrainian government issued a press release saying the experts had reviewed photos of the crash scene.
As the investigation on the ground continued, U.S. Secretary of State John Kerry said there's no shortage of evidence that shows pro-Russian rebels shot down a Malaysian jet in Ukraine last week,
Malaysia Airlines Flight 17 fell from the sky in Donetsk on Thursday, killing all 298 people aboard.
There's video of a launcher with one surface-to-air missile missing, imagery showing the firing and intercepted calls with rebels claiming credit for the strike, Kerry said.
"We know from intercepts ... that those are in fact the voices of separatists," he told CNN's State of the Union on Sunday. "And now we have a video showing a launcher moving back through a particular area there out into Russia with at least one missing missile on it."
Kerry accused Russia of backing the separatists.
"This is the moment of truth for Russia. Russia is supporting these separatists. Russia is arming these separatists. Russia is training these separatists. And Russia has not yet done the things necessary in order to try to bring them under control," he said.
British Prime Minister David Cameron didn't mince words either on who was to blame. In an op-ed in The Sunday Times, he called the plane crash and its aftermath "an outrage made in Moscow."
Russian President Vladimir Putin fired back with a video statement posted on the Kremlin's official website early Monday, arguing that his country has been pushing for peace in Ukraine.
"We have repeatedly called on all parties to immediately stop the bloodshed and to sit down at the negotiating table. We can confidently say that if June 28 fighting in eastern Ukraine did not resume, this tragedy most likely would not have happened," he said. "However, no one should have the right to use this tragedy to achieve selfish political objectives. Such events should not divide but unite people."
He stressed that safety must be guaranteed for international experts investigating the crash.
"We must do everything to ensure their work has full and absolute security (and) ensure necessary humanitarian corridors are provided," Putin said.
At the crash site, there were concerns the bodies had been picked over by thieves.
"The facts of looting, how the terrorists are dealing with the bodies, are beyond the moral boundaries," Ukrainian President Petro Poroshenko tweeted.
The local head of the rebels rejected accusations that his forces shot down the plane, denied accusations that they removed the bodies and denied responsibility when asked about people reportedly using stolen bank-issued cards taken from the victims' bodies.
"It is possible that some local residents could have searched the bodies of victims, found their cards and tried to use them. Unfortunately, I can't exclude the possibility of this," Alexander Borodai said Saturday.
Bodies kept in refrigerated train cars
After preventing international observers from accessing the site, there were small signs of improvement Sunday.
"Today was a better day for sure," said Michael Bociurkiw, a spokesman for the Organization for Security and Co-operation in Europe's monitoring team in Ukraine. "We were able to spend quite a bit of time out at the different crash sites."
But it was still far from a well-organized investigation scene, and the area remained under the control of pro-Russia rebels.
Government emergency workers prevented vehicles from driving up the road to the main crash site, but people could still roam the fields on foot.
Search teams have recovered 272 bodies, 251 of which have been loaded on trains with refrigerators, Ukrainian Prime Minister Arseniy Yatsenyuk said Monday.
Ukraine has sent two trains with four cars but the "bloody guerrillas" will not allow them, he said.
Ukraine is ready to transfer the international investigation over to Dutch team, he said, adding that the bodies will be sent to Amsterdam when they are released. A majority of the victims were from the Netherlands.
Yatsenyuk said 31 international experts arrived in
Kiev, including 23 Dutch, two Germans, two Americans and three Australians.
The Dutch foreign ministry said Dutch forensics have arrived at the trains where the victims' bodies are being kept.
Black boxes found?
Pro-Russia rebels may have recovered the plane's flight data and cockpit voice recorders, their leader Alex Borodai said on the website of the self-declared Donetsk People's Republic.
If experts determine the devices found are the so-called black boxes, they will be turned over to international investigators, according to Borodai.
"These are some technical objects. We cannot say for sure these are black boxes," he told CNN.
Borodai said the devices are under guard in the region. They will not be given to Ukrainian officials, he said.
Reuters distributed video on Sunday of what appeared to be an inflight recorder found by a worker in a field. The agency labeled the video, shot Friday, as showing one of the two flight data recorders from MH17.
Some Malaysian investigators flew to the Ukrainian capital of Kiev on Saturday. But Malaysia's official news agency said they were still negotiating with rebels over access for their team.
Law enforcement officials from the Netherlands, the United States and Australia will help with the investigation led by the Ukrainian government.
Two FBI agents arrived in Kiev, a senior U.S. law enforcement official said. An investigator from the National Transportation Safety Board was also there.
But three days after the deadly crash, it was unclear when an international investigation at the scene would be able to start.
CNN's Phil Black reported from Grabove; Catherine E. Shoichet and Faith Karimi wrote from Atlanta.
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