The claim from UK intelligence sources came as the Moscow-backed separatists yesterday shot down two Ukrainian fighter jets in the east of the country.
British experts have begun their work analysing the black boxes from the flight amid warnings from Australia that some of the bodies of the victims may never be found.
UK government sources yesterday said intelligence showed rebels deliberately tampered with evidence, moving bodies and placing parts from other planes in the debris.
The claims came as fighting continued in eastern Ukraine yesterday, with pro-Russian militia shooting down two military jets just 20 miles from the MH17 crash site. All 298 people on board the Malaysian Airlines flight from Amsterdam to Kuala Lumpur died when the plane was shot down last week.
Some of the bodies have arrived in the Netherlands, where they will be formally identified. But there are warnings that some of the dead may never be recovered.
Home to 193 of the victims, the Netherlands yesterday held a day of national mourning. Flags flew at half-mast on government buildings and family homes.
Six days after the Boeing 777 was shot down, two military transport planes carrying 40 coffins arrived in Eindhoven, where they were met by hundreds of relatives.
“If I have to wait five months for identification, I can do it,” said Silene Fredriksz-Hoogzand, whose son, Bryce, and his girlfriend Daisy Oehlers died in the crash. “Waiting while the bodies were in the field and in the train was a nightmare.”
Speaking at Schiphol Airport, Briton Barry Sweeney had made the same journey to Amsterdam as his son Liam, an avid Newcastle United fan, just six days earlier.
The 28-year-old died alongside fellow Newcastle supporter John Alder as they made their way to see their club on a pre-season tour of New Zealand.
Mr Sweeney said: “We need closure. We need to see our children. All the families, we need them back here.”
But despite the arrival of the bodies, the Australian authorities said some of the victims might never be recovered unless a thorough and secure search area is established.
Referring to the 37 Australians killed, the country’s prime minister, Tony Abbott, said: “My fear is that unless we do more… some of them will never come home.
“It is quite possible that many bodies are still out there in the open in the European summer subject to interference and subject to the ravages of heat and animals.”
Dutch air safety officials leading the investigation into the disaster have still not gained safe access to the crash site.
The Dutch Safety Board (DSB) said analysis of the Malaysia Airlines black box flight recorders, currently being examined by the UK’s Air Accidents Investigation Branch in Hampshire, “may take several weeks”.
But in a report on the on-site investigation, the DSB said: “At the time of writing, the investigators have not yet been able to visit the site of the crash and conduct their investigation under safe conditions.”
Meanwhile, independent military analysts have said that the size, spread, shape and number of shrapnel impacts visible in a photograph of a piece of the wreckage all point to a missile system like the SA-11 Buk.
Justin Bronk at the Royal United Services Institute said: “The size of shrapnel holes is fairly broad, in keeping with what you would expect from a large missile like the SA-11.”