At one stage, the Australian Federal Police mission, headed by Commander Brian McDonald, was seen in deep negotiation with the rebel fighters in Donetsk who regularly escort foreign experts to and from the crash site, about 100 kilometres to the east.

Alexander Hug, deputy leader of an OSCE team that provides operational assistance to foreign experts on the ground, told reporters: "We were planning to go to one of the sites, but security at the site and on the road to it is not acceptable … not appropriate for an unarmed mission such as this."

Flanked by Mr McDonald and his Dutch counterpart, Mr Hug said the investigators were being guided by the separatist fighters. "We have had indications of fighting and we can't take the risk," he said.

Late on Sunday, a spokeswoman for Prime Minister Tony Abbott said that due to heavy fighting, the detachment of Australians and Dutch heading to the crash site had been delayed.

The Ukrainian government had announced a 40 kilometre exclusion zone around the site, in which it had intimated that it would not pursue the Russian-backed rebel forces. But when Fairfax Media drove through the site on Saturday, artillery bombardments could be heard. On Sunday morning, media

crews arriving at rebel checkpoints on the road from Donetsk to the site were turned back.

Mr Hug said he was unable to comment on ''deals made by other parties'' when asked about the deal announced in Kuala Lumpur.

Earlier, Mr Abbott said 11 unarmed Australian police would go to the crash site to secure evidence in what he conceded was a "risky mission".

"Our objective is to get in, get cracking and get out," Mr Abbott said. "This is a risky mission, no doubt about that, but all the professional advice I have is that the safest way to conduct it is unarmed, as part of a police-led humanitarian mission."

Mr Abbott said advice from his special envoy on the ground in Ukraine, retired air chief marshal Angus Houston, was that going into the war-torn area outside Donetsk was "eminently doable". "I've had advice from the Office of National Assessments that while there are risks, they can be mitigated and managed," he said.

AFP Commissioner Tony Negus agreed that the safest way to recover bodies and conduct an air crash investigation in what is expected to be a two- to three-week window is unarmed and without military personnel on site.

In The Hague, Dutch Prime Minister Mark Rutte said: "Getting the military upper hand for an international mission in this area is, according to our conclusion, not realistic," adding it would be a "provocation" that could "destabilise the situation", the BBC reported.

Mr Abbott said on Sunday that he had been in contact with Russian President Vladimir Putin and President Petro Poroshenko of Ukraine in the past 24 hours. He had also had further communications with the prime ministers of the Netherlands and Malaysia.

Mr Abbott was at pains to stress that the police-led mission had "nothing to do with the politics of eastern Europe".

''We will stay as long as we can to do a professional job, but we won't stay a moment longer than we need to," he said.

The hostilities between Ukrainian forces and rebels show no sign of quieting. Government troops fought rebels in Horlivka, just kilometres outside Donetsk, home to the separatist-dubbed ''Donetsk People's Republic.''

The danger did not keep Perth couple Jerzy Dyczynski and Angela Rudhart-Dyczynski from becoming the first family or friends to visit the crash site on Saturday, after the loss of their daughter Fatima, 25.

But the prospect of urban warfare underscores the volatility of eastern Ukraine. Unreleased data from a black box retrieved from the wreckage show findings consistent with the plane's fuselage being hit multiple times by shrapnel from a missile explosion.

''It did what it was designed to do,'' a European air safety official said. ''Bring down airplanes.''