International inspectors have accused people working at the crash site of Malaysia Airlines flight MH17 in Ukraine of damaging the wreckage and failing to collect all the remains of the 298 people on board who died.

The Organisation for Security and Co-operation in Europe (OSCE) made the claims, as some of the victims’ bodies were prepared for repatriation and the US pledged to reveal evidence linking the disaster to pro-Russian rebels in eastern Ukraine.

Washington demanded an international team of experts be given full access to the site in rebel-held territory, and the International Air Transport Association called the slow progress of the investigation an “outrage to human decency.”

Michael Bociurkiw, a spokesman for OSCE monitors who have visited the crash area several times, said the tail fin and other major pieces of the Boeing 777 appeared to have been “cut into”. The monitors said they “saw that one of the largest pieces of debris had been split in two. Elsewhere, a considerable amount of smaller debris appeared to have been moved.”

Western leaders have denounced the handling of the crash site by rebels, whom they say appear to be tampering with and perhaps destroying evidence that could be crucial to discovering what brought down the plane en route from Amsterdam to Kuala Lumpur last Thursday.

“After the crime, comes the cover-up. What we have seen is evidence-tampering on an industrial scale,” said Australian prime minister Tony Abbott. Twenty-eight Australians died on the aircraft, which Kiev insists was brought down by a surface-to-air missile given to the rebels by Russia.

“We observed the presence of smaller body parts at the site,” Mr Bociurkiw said, hours after a train carrying the remains of about 200 passengers arrived in government-controlled territory.

“We’ve never really seen that intensive combing over the site – people arm-in-arm going over the fields,” Mr Bociurkiw said, noting there was in effect no security at the site and only a few international experts had visited it.

The US last night called for investigators to be given “immediate and full access”. “I don’t think we’ve seen yet the level of co-operation with international investigators that we’d like to see,” said spokesman Josh Earnest.

Repatriating bodies

Russia and the militants blame Kiev for the disaster.

Kremlin leader Vladimir Putin said he would “do everything” to influence the separatists and ensure a full investigation, but also urged western powers to press Ukraine’s government to call a ceasefire.