Almost two weeks after Malaysia Airlines Flight MH17 was blown out of the sky, the remains of some passengers are feared rotting in the 32 C midsummer heat, deepening the frustration of relatives desperate to recover the bodies of their loved ones.

Fighting between Ukrainian forces and separatist rebels has kept away international police charged with securing the site, a sprawling area of farmland and villages. And until it's secured, there is no way for forensic experts to recover the bodies or gather debris for analysis.

Even the rebels -- who initially oversaw the collection of more than 200 of the 298 bodies in a disorganized, widely criticized effort -- have stopped their work, saying attacks from the Ukrainian military have forced them to focus on defending themselves.

It remains unclear exactly how many bodies remain and what condition they are in after being exposed for so long to the elements. Dutch officials are adamant there are still bodies to be recovered, and Prime Minister Mark Rutte has said repeatedly that bringing them back is his government's top priority.



But Dutch officials were gloomy Wednesday about the prospects of reaching the site any time soon.



"We don't expect the security situation to improve enough over the next few days to make this possible," said Pieter-Jaap Aalbersberg, head of the Dutch-led recovery mission.

Australia's prime minister and foreign minister on sent mixed messages on whether Russia was frustrating Dutch and Australian police efforts.

Foreign Minister Julie Bishop said she feared Russia was behind the daily artillery barrages blocking police, while Prime Minister Tony Abbott said it was too early to judge. Abbott has declined to follow the U.S. and European examples by ratcheting up sanctions against Russia in a bid to pressure President Vladimir Putin into ending his country's support for the separatists.

Bishop said the remains of 80 of the 298 people killed when Malaysia Airlines Flight 17 was shot down on July 17 could remain at the crash site, which is being fiercely fought over by Ukraine and Russian-backed separatists.

"My great fear is Russia is actively undermining this process. We've had the strongest possible support from the Ukrainian government but still the fighting goes on and there is no ceasefire," Bishop told Australian Broadcasting Corp. from Kiev.

"Whilst I can't point my finger at who starts the shelling, we get absolute assurances from the Ukraine government that it's not them," she said, adding that intelligence suggested missiles came from the Russian side.

Asked whether Russia was frustrating police efforts, Abbott told Melbourne Radio 3AW: "I think Russia is pursuing its own interests."

"But I suspect that it is at least partly in Russia's interests at this time to ensure that our police mission successfully goes ahead," Abbott added.

Crucial evidence retrieved

Two crucial pieces of evidence -- the flight recorders -- have already been retrieved and analyzed, however.



The U.S. and Ukrainian governments say the Boeing 777 was brought down July 17 by a Russian-made missile fired by eastern Ukraine's pro-Moscow separatists. The separatists deny it; Russia denies providing the Buk missile launcher and says the Ukrainian military may have shot the plane down.



After the investigative team's failure to reach the site on Wednesday, the United Nations called on both sides in Ukraine's grinding civil conflict to cease hostilities in the area.

The families of the victims of this horrific tragedy deserve closure and the world demands answers. - UN spokesman Stephane Dujarric

"The families of the victims of this horrific tragedy deserve closure and the world demands answers. International teams must be allowed to conduct their work," UN spokesman Stephane Dujarric said.



In their latest attempt to get to the wreckage zone, observers from the Organization for Security and Cooperation in Europe left in two vehicles from the rebel-held city of Donetsk but got only as far as the city's outskirts.



The observers talked with rebels and turned back after being "warned of gunfire on the route and in the surrounding areas," the Dutch said in a statement.



Recent offensives by the Ukrainian army have enabled it to take back swaths of territory from the rebels. But the fighting has edged ever closer to the crash zone.



"We are still waiting and it is a miserable process," said Jasmine Calehr, the grandmother of two Dutch brothers who died in the crash



International observers say wreckage has been cut, moved or otherwise tampered with.



Of the 298 who died, 194 were Dutch citizens, and Ukraine has asked for their government's help in investigating the crash. Thirty-seven were from Australia. A total of 227 coffins have been flown to the Netherlands for identification and investigation.



Despite her mounting frustration, Calehr said she did not want investigators to go unless it was safe.



"Other people are not supposed to risk their lives," she said. "But that there is nobody strong enough to put pressure on a bunch of rebels is very painful."

Ukraine claims crash area mined

Ukrainian government security spokesman Andriy Lysenko added to security concerns Wednesday by accusing the separatists of mining the approaches to the area. Even if rebels leave, he said, it will take time to remove the mines and make the area safe for investigators.



Meanwhile, the head of Ukraine's security services revealed what he said was fresh satellite imagery proving Russia had created a major cross-border corridor for the delivery of military equipment to the rebels.



Valentyn Nalyvaichenko said other photographs showed burn marks from rockets fired at Ukrainian troops from a position two kilometers inside Russian territory.