International teams of investigators and monitors moved gingerly Saturday through fields littered with debris and decomposing corpses of the victims of a Malaysia airliner shot down over rebel-held eastern Ukraine, as they try to secure the sprawling site in hopes that a credible investigation can be conducted.

Malaysia Transport Minister Liow Tiong Lai said at a news conference Saturday in Kuala Lumpur that "the integrity of the site has been compromised, and there are indications that vital evidence has not been preserved in place." He called for immediate access for Malaysia's team at the site to retrieve human remains of the 298 victims, and said "we need the support of the world to ensure that the site is not tampered, that we have access to the site."

The crash that killed all 298 people aboard Malaysia Airlines flight MH17 Thursday intensified the already-high animosity on all sides of the conflict as pro-Russian separatists and the Ukrainian government traded charges about who was responsible for shooting down the Boeing 777 with a surface-to-air missile.

The Ukrainian government accused Russia of assisting separatist rebels in destroying evidence at the site, saying militiamen have removed 38 bodies from the area and have taken them to the rebel-held city of Donetsk. It says 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.

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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.

On Saturday, in the village of Hrabove, one passenger's body was seen still strapped into an airline seat, with bare toes peeking out under long jeans. Another body was flung face-up into a field of blue flowers.

Treatment of the victims' remains, left in the open air under a hot summer sun punctuated by bursts of rainfall, has provoked outrage and distress.

"The news we got today of the bodies being dragged around, of the site not being treated properly, has really created a shock in the Netherlands," Dutch Foreign Minister Frans Timmermans told the Ukrainian president in Kiev. "People are angry, are furious at what they hear."

Timmermans demanded the culprits be found. "Once we have the proof, we will not stop until the people are brought to justice," he said. The flight manifest showed 193 of the 298 passengers and crew killed were Dutch.

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.

German Chancellor Angela Merkel and Russian President Vladimir Putin agreed on Saturday that an independent, international commission led by the International Civil Aviation Organization, ICAO, should be granted swift access to the crash site, German government spokesman Georg Streiter and the Kremlin said. Streiter said Merkel urged Putin to use his influence of the separtists to make that happen.

Though aviation experts say not to expect too much from the flight data and cockpit recorders in understanding how MH17 was brought down, the location of the boxes remains a mystery. Separatist leadership remained adamant that it hadn't located them.

Michael Bociurkiw, a spokesman for the Organization for Security and Co-operation in Europe's monitoring mission in Ukraine, which has a 24-member delegation that was given limited access to the site, also said he had received no information on their whereabouts.

Bociurkiw said the team was given further access to the site, but their movements were being limited by the rebels. He stressed that his team was not at the site to conduct a full-scale investigation.

"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."

Meanwhile, a well-placed source with access to the latest intelligence told Fox News that the missile launcher used to down the plane is probably back in Russia after it was imported into Ukraine a few weeks ago. The same source said the missile was fired from Schnidze, a town in eastern Ukraine.

At an emergency meeting of the U.N. Security Council on Friday, 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."

A report by the Daily Mail showed the BUK SA-11 launcher used in the attack missing two of its four missiles. A senior U.S. defense official confirmed the newspaper's report.

"We are building a case," the official told Fox News. "It is damn near bulletproof at this point."

Obama called the downing of the plane "a global tragedy," adding that at least one American was among the passengers killed aboard the flight. Obama said the plane appears to have been downed by a missile launched from Ukraine by pro-Russian separatists.

Igor Strelkov, the local separatist commander who likely ordered the strike and who was heard in phone intercepts released by the Ukrainian Interior Ministry bragging about having brought down the plane, will likely be punished by Moscow, according to a well-placed source.

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.

Click here to read more from the Daily Mail and Sky News.

Fox News' Jennifer Griffin and The Associated Press contributed to this report.