Members of the media take pictures as a pro-Russian separatist places black boxes belonging to Malaysia Airlines flight MH17 on a desk, before their handover to Malaysian representatives in Donetsk, July 22, 2014. [Photo/Agencies]

Recovery efforts

European security monitors said gunmen stopped them inspecting the site when they arrived on Friday, and Ukrainian officials said separatists had tampered with vital evidence, allegations echoed by Obama.

But the spokesman for the European security monitors said they had unfettered access on Monday, and three members of a Dutch disaster victims identification team arrived at a railway station near the crash site and inspected the storage of the bodies in refrigerated rail cars.

Peter van Vliet, whose team went through the wagons dressed in surgical masks and rubber gloves, said he was impressed by the work the recovery crews had done, given the heat and the scale of the crash site. "I think they did a hell of a job in a hell of a place," he said.

As they went about their work, fighting flared in Donetsk, some 60 km (40 miles) from the site, in a reminder of the dangers the experts face operating in a war zone.

The government in Kiev denied sending the regular army into the centre of Donetsk, which pro-Russian separatists captured in April, but said small "self-organised" pro-Ukrainian groups were fighting the rebels in the city.

Four people were killed in clashes, health officials said.

The rebels' military commander Igor Strelkov said on his Facebook page up to 12 of his men died in Monday's fighting.

Donetsk is at the heart of a rebel uprising against rule by Kiev, and Ukrainian President Petro Poroshenko has vowed to retake the city as part of what Kiev calls its "anti-terrorist operation" against the separatists.

Television images of the rebel-controlled crash site, where the remains of victims had lain decomposing in fields among their personal belongings, have turned initial shock and sorrow after Thursday's disaster into anger.

Australian Prime Minister Tony Abbott said an Australian investigation team was in Kiev but had been unable to travel to the site. He said there had been some improvement with the Ukrainian government offering access.

"But there's still a hell of a long way to go before anyone could be satisfied with the way that site is being treated," Abbott said. "It's more like a garden cleanup than a forensic investigation. This is completely unacceptable."