MOSCOW (AP) — Russian President Vladimir Putin lashed out Monday against those who he said were exploiting the downing of a passenger jet in eastern Ukraine for "mercenary objectives."

Putin said Russia was doing everything possible to allow a team of experts from the International Civil Aviation Organization, a U.N. agency, to investigate the scene. He also again criticized the Ukraine authorities in Kiev for reigniting the fighting with the pro-Russian rebels who control the crash site.

"We can say with confidence that if fighting in eastern Ukraine had not been renewed on June 28, this tragedy would not have happened," Putin said. "Nobody should or does have a right to use this tragedy for such mercenary objectives."

Putin is coming under increasing international pressure to rein in the rebels in Ukraine and allow international inspectors to investigate the crash site of Malaysia Airlines Flight 17, which was downed Thursday over Ukraine, killing all 298 people aboard.

On Sunday, the United States presented what it called "powerful" evidence that the rebels shot down the plane with a Russian surface-to-air missile.

"Russia is supporting these separatists. Russia is arming these separatists. Russia is training these separatists," Secretary of State John Kerry said on CNN's 'State of the Union.'

The leaders of Britain, France, Germany and Australia also spoke to Putin by phone late Sunday. European foreign ministers are also meeting in Brussels Tuesday to consider further sanctions on Russia.

International indignation has grown as investigators still only have limited access to the sprawling fields where the plane fell.

Pro-Moscow rebels piled nearly 200 bodies from the downed Malaysian jetliner into four refrigerated boxcars Sunday in eastern Ukraine, and cranes at the crash scene moved big chunks of the Boeing 777, drawing condemnation that the site was being tampered with.

In an opinion piece for the Sunday Times, British Prime Minister David Cameron said there was a "growing weight of evidence" suggesting that the rebels shot down the plane.

If that was the case, Cameron said that was "a direct result of Russia destabilizing a sovereign state, violating its territorial integrity, backing thuggish militias and training and arming them."

Australian Prime Minister Tony Abbott, whose country lost 28 citizens in the tragedy, said Putin "said all the right things" during their telephone conversation about ensuring an international investigation into the disaster.

"I'm now going to try to ensure that as far as Australia humanly can, we insist upon these things happening," Abbott told Sydney Radio 2GB on Monday. "The site is being treated more like a garden cleanup than a forensic investigation, and this is completely unacceptable."

The 109-square-kilometer (42-square-mile) crash site, spread out on farmland and villages, looked dramatically different Sunday, a day after armed rebels had stood guard while dozens of bodies lay in the summer heat. The rebels were gone, and 192 bodies were loaded into the refrigerated train cars in the rebel-held town of Torez, 15 kilometers (nine miles) away.

The Ukrainian government said in a statement on its website that a second train with four refrigerator cars had arrived at Torez station.

Emergency workers, who the rebels have allowed to operate under their control, were searching the sprawling fields. Cranes moved pieces of the plane around, apparently to look for more bodies underneath.

By Sunday night, Ukraine's emergency services agency said the total number of bodies found was 251.

Dutch Prime Minister Mark Rutte, whose country lost 192 citizens on the plane, told a news conference that repatriating the bodies was his "No. 1 priority."

He said all efforts were aimed at getting the train with the bodies to "territory controlled by Ukraine" and that a Dutch military plane was being sent to Kharkiv to set up a coordination center.

Michael Bociurkiw, a spokesman for the Organization for Security and Cooperation in Europe, said reports from the group's investigators in Ukraine suggest some bodies were incinerated without a trace.

"We're looking at the field where the engines have come down. This was the area which was exposed to the most intense heat. We do not see any bodies here. It appears that some have been vaporized," he said from the crash site.

Rebel leader Alexander Borodai denied the rebels were trying to tamper with evidence, saying the bodies would be turned over to a team of Malaysian experts he was expecting.

A group of investigators that included Malaysian officials was in Kiev, but said they wouldn't go into rebel-held areas until they get better assurances about security. The Ukrainian government, which has responsibility for the investigation, has also asked for help from the International Civil Aviation Organization — a U.N. body — and Eurocontrol, a European air traffic safety organization.

Borodai insisted the rebels have not interfered with the investigation, and said he would turn over the plane's flight data and cockpit voice recorders, or "black boxes," as well.

"The bodies will go nowhere until experts arrive," Borodai said in the rebel-held city of Donetsk.

But there were clear indications that the rebels were interfering in the investigation.

Lyubov Kudryavets, a worker at the Torez morgue, said that on the evening the plane went down, a resident brought in the bloodied body of a child, about 7 or 8 years old. On Saturday, militiamen came to take away the body away, she said.

"They began to question me: 'Where are the fragments of rocket? Where are the fragments from the plane?'" Kudryavets said. "But I didn't have any wreckage. ... I swear."

Experts said that even if investigators are granted access now, it might be too late.

"Even without any deliberate attempt at a cover-up, the crash site is already compromised in forensic terms," said Keir Giles, an associate fellow at the Chatham House think tank. "A reconstruction of the aircraft fuselage and wings would give a picture on how the missile struck and what kind it was. If any aircraft parts have already been removed ... this compromises the objectivity of the investigation."

Rutte said the Dutch foreign minister was headed to the U.N. to lobby "to further expand the international coalition pushing for quick recovery of the bodies and getting to the bottom of the terrible events on MH17."

In the Netherlands, worshippers at church services prayed for the victims, as anger grew over the rebels' hindering of the investigation.

Silene Fredriksz-Hoogzand, whose son, Bryce, and his girlfriend, Daisy Oehlers, were among those killed, said she was appalled their bodies weren't being handed over.

"Mr. Putin, send my children home," she said, speaking on Sky TV from Amsterdam's Schiphol Airport. "Send them home. Please."

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Peter Leonard in Kiev; Nataliya Vasilyeva in Moscow; Nicholas Garriga in Hrabove, Ukraine; Lucian Kim in Kharkiv, Ukraine; Michael Corder in The Hague, Netherlands; Danica Kirka in London, Lolita C. Baldor in Washington and Rod McGuirk in Canberra, Australia, contributed to this report.