HRABOVE, Ukraine -- Ukraine accused Russia on Saturday of helping separatist rebels destroy evidence at the crash site of a Malaysia Airlines plane shot down in rebel-held territory -- a charge the rebels denied.
As dozens of victims' bodies lay in bags by the side of the road baking in the summer heat, international monitors at the crash site Saturday said they were still being hampered by heavily armed rebels.
"Some of the body bags are open and the damage to the corpses is very, very bad. It is very difficult to look at," OSCE spokesman Michael Bociurkiw told reporters in a phone call from the site, where the smell of decaying bodies was unmistakable.
He said the 24-member delegation was given further access Saturday to the crash site but their movements were being limited by the rebels. The site sprawls eight square miles (20 square kilometers) across sunflower and wheat fields between two villages in eastern Ukraine.
"We have to be very careful with our movements because of all the security," Bociurkiw said. "We are unarmed civilians, so we are not in a position to argue with people with heavy arms."
Flight 17 from Amsterdam to Kuala Lumpur was carrying 298 people from 13 nations when it was shot down Thursday in eastern Ukraine close to the Russian border, an area that has seen months of clashes between government troops and pro-Russia separatists.
At an emergency meeting of the U.N. Security Council, the U.S. pointed blame at the separatists, saying Washington believes the jetliner likely was downed by an SA-11 missile and "we cannot rule out technical assistance from Russian personnel."
The government in Kiev said militiamen have removed 38 bodies from the crash site and have taken them to the rebel-held city of Donetsk. It said the bodies were transported with the assistance of specialists with distinct Russian accents.
The rebels are also "seeking large transports to carry away plane fragments to Russia," the Ukrainian government said in a statement Saturday.
In Donetsk, separatist leader Alexander Borodai denied that any bodies had been transferred or that the rebels had in any way interfered with the work of observers. He said he encouraged the involvement of the international community in assisting with the cleanup before the conditions of the bodies worsens significantly.
As emergency workers put some 80 bodies into bags Saturday, Bociurkiw stressed that his team was not at the site to conduct a full-scale investigation.
"We are looking at security on the perimeter of the crash site, looking at the status in the condition of the bodies, the status in the condition of the debris, and also personal belongings," he said.
Ukraine also called on Moscow to insist that the pro-Russia rebels grant international experts the ability to conduct a thorough, impartial investigation into the downing of the plane -- echoing a demand that President Barack Obama issued a day earlier from Washington.
"The integrity of the site has been compromised, and there are indications that vital evidence has not been preserved in place," Malaysian Transport Minister Liow Tiong Lai said at a news conference in Kuala Lumpur.
He called for immediate access for Malaysia's team at the site to retrieve human remains.
Ukraine says it has passed along all information on developments relating to Thursday's downing to its European and U.S. partners.
German Chancellor Angela Merkel and Russian President Vladimir Putin agreed in a phone call Saturday that an independent, international commission led by the International Civil Aviation Organization, ICAO, should be granted swift access to the crash site, said government spokesman Georg Streiter.
The commission should examine the circumstances of the crash and recover the victims, said Streiter, adding that Merkel urged Putin to use his influence over the separatists to make that happen.
In the Netherlands, forensic teams fanned out across the country Saturday to collect material including DNA samples that will help positively identify the remains of the 192 Dutch victims.
Police said in a tweet that 40 pairs of detectives from the National Forensic Investigations Team would be visiting victims' relatives over the coming days.
The location of the black boxes remains a mystery and the separatist leadership remained adamant Saturday that it had not located them. Bociurkiw also said he had received no information on their whereabouts.
Aviation experts say, however, not to expect too much from the flight data and cockpit voice recorders in understanding how Flight 17 was brought down.
The most useful evidence that's likely to come from the crash scene is whether missile pieces can be found in the trail of debris that came down as the plane exploded, said John Goglia, a U.S. aviation safety expert and former National Transportation Safety Board member.
The operation of the Flight 17 doesn't appear to be an issue, he said.
Obama called the downing of the plane "a global tragedy."
"An Asian airliner was destroyed in European skies filled with citizens from many countries, so there has to be a credible international investigation into what happened," he said.
Both the White House and the Kremlin have called for peace talks in the conflict between Ukrainian government forces and Russian-speaking separatists who seek closer ties to Moscow. Heavy fighting took place Friday around Luhansk, less than 100 kilometers (60 miles) from the crash site, with 20 civilians reported killed.
Malaysia Airlines, meanwhile, said Saturday it has no immediate plans to fly the relatives of the 298 passengers and crew killed to visit the crash site in Ukraine because of security concerns.
A spokesman for the airline says next of kin are being cared for in Amsterdam while a team from the carrier, including security officials, was in Ukraine assessing the situation.
In the Netherlands, travelers flying out of Amsterdam's Schiphol Airport laid flowers and signed a condolence book before boarding their flights Saturday, including those on the latest Malaysia Airlines Flight 17 to Kuala Lumpur.
David McHugh in Kiev, Ukraine; Mstyslav Chernov in Donetsk, Ukraine; Michael Corder in Amsterdam and Frank Jordans in Berlin contributed to this report.