WASHINGTON  - Russia supplied sophisticated missile launchers to separatists in eastern Ukraine and that attempts were made to move them back across the Russian border after the Thursday shoot-down of a Malaysian jet liner, according to new US intelligence assessments.

“We do believe they were trying to move back into Russia at least three Buk [missile launch] systems,” a US official was quoted as saying in American media reports published on Sunday. US intelligence was “starting to get indications . . . a little more than a week ago” that the Russian launchers had been moved into Ukraine, the official said.

Of the 298 people on Malaysia Airlines Flight 17, remains of some 100 passengers are still missing. The Ukrainian government has criticized lack of full access to the site in an area controlled by pro-Russian rebels.

The Ukrainian government presented videos as evidence that pro-Russian separatists in eastern Ukraine are to blame for shooting down Malaysia Airlines plane, the reports said. The expanding case against the Ukrainian separatists and Russia comes as US and Western leaders have swapped rounds of phone calls since Friday, calling for greater pressure against Moscow and a renewed effort to secure the chaotic crash site in eastern Ukraine and ensure that human remains receive proper attention. Secretary of State John Kerry phoned his Russian counterpart on the issue Saturday.

The added certainty that the SA-11 systems likely were in rebel hands also poses questions about why Ukraine or US officials didn’t move more quickly to advise commercial jetliners of potential dangers, if there was time after they learned of possible rebel control of the systems, The Wall Street Journal commented. Moscow has continued to deny supplying armed separatists with heavy weapons. “We know there are Russian troops inside Ukraine,” a US official was quoted as saying. “Russian troops, Russian equipment.”

Russian President Vladimir Putin has expressed condolences to families for the shoot down, but said that the Ukrainian government is responsible for failing to keep the peace in its eastern provinces. The Kremlin has stopped short of blaming Ukraine’s military for the catastrophe.

No expert air crash investigators have yet had access to the rural crash site since Flight 17 was shot down on Thursday afternoon, and in the absence of an independent investigation US and regional intelligence officials have been poring over satellite and electronic intercepts seeking clues about the cause of the crash.

AFP adds: Pro-Russian militiamen in Ukraine loaded almost 200 bodies from the downed Malaysian jet into trains on Sunday and said they had recovered objects from the crash site believed to be the plane’s black boxes.

Grieving families were clamouring to have their loved ones brought home, as concerns mounted that the rebels were still limiting access to the bodies and hiding key evidence from Thursday’s disaster. European leaders again warned Russia to ensure rescuers and investigators have full and unfettered access to the crash site in rebel-held eastern Ukraine or face further EU sanctions.

Malaysia Airlines flight MH17 was blown out of the sky by what is believed to be a surface-to-air missile, killing at 298 passengers and crew and dramatically raising the stakes in Ukraine’s bloody three-month conflict.

“Jet parts resembling the black boxes were discovered at the crash site,” said Alexander Borodai, prime minister of the self-proclaimed Donetsk People’s Republic, adding that they would be handed over to “international experts if they arrive”.

OSCE monitors escorted by armed rebels appeared Sunday to be granted greater freedom to examine the site in Grabove.

Borodai said the fighters had moved scores of bodies “out of respect for the families” and loaded them on to trains where they would be kept in refrigerated carriages until “the experts arrive”.

“We couldn’t wait any longer because of the heat and also because there are many dogs and wild animals in the zone.”

The OSCE observers said they found the corpses packed into refrigerated wagons at a station in the town of Torez, some 15 kilometres (nine miles) from the crash site.

Spokesman Michael Bociurkiw described the stench at the station, where armed separatists were guarding the grisly cargo, as “almost unbearable”.

The bodies, some dismembered and charred, had been left rotting in cornfields amid the blackened piles of mangled wreckage of the plane, with debris spread out for kilometres.

An AFP crew found the scene largely abandoned Sunday, with all bodies removed and the discarded gloves of emergency workers scattered around along with the possessions of the victims: suitcases torn open, passports, books, children’s toys.

World leaders have demanded Russian President Vladimir Putin use his influence to persuade the rebels to hand over the victims and allow international investigators full access.

“Russia must understand that resolving the Ukrainian crisis is more than ever an imperative after this tragedy which has outraged the entire world,” the French presidency said after President Francoise Hollande held separate telephone talks with the British and German leaders.

A Downing Street spokesman said the three leaders had agreed 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”.

Kiev and the West have accused Moscow of providing the Ukrainian rebels with the missile launchers that blasted the plane out of the sky.

US Secretary of State John Kerry said it was “pretty clear that this is a system that was transferred from Russia in the hands of separatists,” while slamming as “grotesque” scenes at the crash site.

Ukrainian Prime Minister Arseniy Yatsenyuk told a German newspaper that such an operation would take professionals and not “drunken gorillas”.

The Washington Post said Vitaly Nayda, Ukraine’s counterintelligence chief, had photographs and related evidence that three Buk M-1 anti-aircraft missile systems moved from rebel-held territory into Russia early Friday, less than 12 hours after the plane was downed.

Ukraine has released recordings of what it said was an intercepted call between an insurgent commander and a Russian intelligence officer as they realised they had shot down a passenger jet.

But top Russian officials and state media have suggested that Kiev’s new leaders staged the attack to blame the rebels and convince their Western allies to deploy troops and help seal Ukraine’s porous border with its giant eastern neighbour.

Dutch Prime Minister Mark Rutte - his shocked nation flying flags at half mast in mourning over 193 lost compatriots - urged Putin to “take responsibility” for a credible probe.

Across the globe relatives in the dozen countries whose citizens were killed when the Boeing 777 crashed en route from Amsterdam to Kuala Lumpur pleaded for them to be brought home.

“At this current moment I hope the world can assist the families to bring back the remains,” Zulkifli Abdul Rahman, brother-in-law of one of the cabin crew, told AFP in Kuala Lumpur.

The disaster has an added poignancy for Malaysia after the March disappearance of the Kuala Lumpur to Bejing flight MH370 with 239 passengers and crew on board.

Across the Netherlands, churchgoers prayed for the dead at memorial services.

“What should have been the ushering in of a wonderful holiday time has become a nightmare,” Father Wim van Meijgaarden said in the southern town of Meerssen.

Putin has denied exerting any influence over the rebels, who had sent an email to the media on Sunday saying they would only accede to Western demands over the crash if Kiev agrees to a truce to end months of fighting in the east.

Ukrainian President Petro Poroshenko ripped up a shaky ceasefire on July 1 and has refused to announce a new one until the separatists who launched an uprising against Kiev in the wake of Moscow’s controversial annexation of Crimea in March give up their arms.

Poroshenko spent much of the day Saturday pressing world leaders to recognise the militias as a terrorist organisation that should be put on trial at the International Criminal Court in The Hague.

He told France’s Hollande that the downing of flight MH17 was similar to such atrocities as the 2001 attacks on the United States.

“We see no difference between the events in Ukraine and what happened on September 11 in the United States or the tragedy over Scotland’s Lockerbie,” Poroshenko said in reference to the 1988 bombing of Pan Am Flight 103 that claimed nearly 300 lives.

The MH17 disaster came after the United States unleashed punishing sanctions against some of Russia’s biggest military firms - most of them with links to Putin.