Two months ago while coming into land at Donetsk airport, I found myself gazing out from the aircraft window at the flat steppe landscape of Eastern Ukraine that lay below.

From thousands of feet up, the ground beneath was a patchwork montage of wheat fields and forests. Tranquil from this altitude, it was hard to believe that I was about to enter a war zone.

Even harder to imagine would have been the terrible last moments of passengers aboard Malaysia Airlines flight MH17, who, it now it seems, have become the unlikely victims of Ukraine's conflict after being blown from the sky by an anti-aircraft missile on Thursday.

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This weekend, the political fallout from this tragedy is strewn across the globe just as the bodies and belongings of its victims litter the sunflower fields of the land that lies between the Luhansk and Donetsk regions of this troubled country.

As loved ones of the victims mourn their loss, the questions have begun. Was the airliner for certain shot from the sky and if so by whom? And should that prove to be the case, how will those responsible be brought to account?

Any answer to the first of these questions, is proving difficult to ascertain as separatist rebels continue to prove obstructive to independent crash investigators and monitors from the Organisation for Security and Co-operation in Europe (OSCE).

At one point yesterday OSCE observers found their access hampered by armed men from the forces of the self-declared People's Republic of Donetsk.

In sometimes tense scenes with the separatist fighters clearly uncomfortable at having observers and the press present, one journalist told of how he heard a senior rebel tell the OSCE delegation they could not approach the wreckage and would be informed in due course of an investigation conducted by the separatists

Amid reports of looting by separatist fighters, local people and emergency workers say they have been doing their best to collect evidence and preserve human remains.

The Ukrainian security council in Kiev said staff of the emergencies ministry had found 186 bodies and had checked some seven square miles of the scattered crash site. But the workers, they said, were not free to conduct a normal investigation.

"The separatists have let the Emergencies Ministry workers in there, but they are not allowing them to take anything from the area," security council spokesman Andriy Lysenko said. "The fighters are taking away all that has been found."

As the stench of decaying corpses began to pervade the area, rescue workers carried bodies across the fields and gathered remains in black sacks. In many areas, though, international investigators were still being blocked and kept on the sidelines by separatist gunmen.

"We had expected unfettered access, that's the way we work," Michael Bociurkiw, an OSCE representative said after an earlier attempt to gain access to the crash site on Friday.

The armed men his team encountered he described as "impolite and unprofessional" and some were suspected of being drunk.

For their part the separatists claim they have avoided disturbing the area where the plane crashed.

"There's a grandmother. A body landed right in her bed. She says 'please take this body away'. But we cannot tamper with the site," insisted Alexander Borodai, the self-proclaimed prime minister of the Donetsk People's Republic.

"Bodies of innocent people are lying out in the heat. We reserve the right, if the delay continues ... to begin the process of taking away the bodies. We ask the Russian Federation to help us with this problem and send their experts," Borodai added.

The separatist leader's remarks only further fuelled the suspicions of both the Ukrainian government and other international political leaders many of whom now say there is a solid body of intelligence evidence that the missile was fired from separatist positions.

"The terrorists, with the help of Russia, are trying to destroy evidence of international crimes," the Ukrainian government said in a statement.

"The terrorists have taken 38 bodies to the morgue in Donetsk," it said, accusing people with "strong Russian accents" of threatening to conduct autopsies.Ukraine's prime minister said armed men barred government experts from collecting evidence and threatened to detain them.

Yesterday, Ukrainian counter intelligence chief Vitaly Naida said he had "compelling evidence" that not only had the SA-11 Buk radar-guided missile system Kiev says was used to hit the airliner been brought over the border from Russia, but the three-man crew was also comprised of Russian citizens.

He said the unit had returned to Russia and demanded Moscow let Kiev question them.

In Washington, US officials describe as convincing audio recordings that the Ukrainian government has released purporting to be of Russian officers and rebels discussing shooting down the plane.

Moscow has repeatedly denied Kiev's accusations that it is supplying manpower and hardware across the frontier to the rebels. If there is now little doubt that a missile did bring down flight MH17 and that it was fired by separatists rebels, the questions that follow will focus on what impact the resulting crisis will have on the separatist cause, their relations with Moscow and whether those responsible can be brought to justice.

While most of the rebel fighters are locals, the rebellion is, for all intents and purposes, a Russian creation. Time and again during my time in eastern Ukraine a few months ago that much became clearer by the day. Now, journalists and intelligence analysts alike have been confronted with stark and substantial evidence that Moscow's presence has been all pervasive. The Kremlin, of course, has tried hard to present another face of its involvement but as analysts for the influential US based magazine have pointed out, Russia has consistently "encouraged, facilitated, and protected the rebels while maintaining an official air of detachment".

Even yesterday in the wake of the crash and the controversy surrounding it, Ukrainian government officials were insisting that such material support was still ongoing.

"During the night, 15 pieces of military equipment were brought from the side of the Russian Federation onto the territory of the Luhansk region," said a spokesman for the country's security council, adding that separatists had also brought equipment to the plane crash site to remove debris.

For some weeks now compelling evidence has emerged that the Russians have been upping the military ante on the battlefields of the region launching short-range rocket strikes on Ukrainian positions, after the rebels lost their stronghold town of Sloviansk during an offensive by Ukrainian forces.

Kremlin support also came in the shape of heavy weapons, artillery and armoured vehicles. This supply chain may well have included the Buk surface-to-air (SAM) missile system that is believed to have brought down MH17.

On another level, however, there have also been a few signs that Moscow has been increasingly irritated by its separatist proxies.

The measure of this can be gauged by the Kremlin's recent attitude to Igor Girkin, aka Strelkov, the separatists' self-proclaimed "minister of defence". Once Moscow's man on the ground in eastern Ukraine, Strelkov is said to hold the rank of reserve colonel and is most likely connected to Russian intelligence. Certainly, in the past, he has served in shadowy roles in Bosnia, Transnistria and Chechnya.

Strelkov, however, has been grumbling a lot of late about what he saw as dwindling of support from his Moscow backers. Apparently overstepping the mark, he incurred the wrath of Eduard Bagirov, one of president Vladimir Putin's political henchmen who warned the separatist leader that he would be "squashed like a flea" if he didn't toe the line.

The problem for the Kremlin is that it has created something of a Frankenstein's monster in the shape of people like Strelkov and its separatist proxies in eastern Ukraine. Slowly but surely Russian intelligence agencies appear to have lost a degree of control leaving some rebel fighters as loose cannons. This in part may go some way to explaining why a missile was launched by rebels without an effective command structure with the tragic consequences of bringing down flight MH17.

Whatever the truth, for once it seems President Putin finds himself between a rock and a hard place on the global diplomatic arena.

Some observers believe the scale of the disaster could prove a turning point for international pressure to resolve the crisis in Ukraine, which has killed hundreds since pro-Western protests toppled the Moscow-backed president in Kiev in February and Russia annexed the Crimea peninsula a month later.

"This outrageous event underscores that it is time for peace and security to be restored in Ukraine," insisted President Barack Obama in the wake of the plane's crash, adding that Russia had failed to use its influence to curb rebel violence.

Obama's remarks that the loss of flight MH17 is a "wake-up call" to Europe to join the United States in threatening Moscow with heavier economic sanctions if it does not help end the conflict, in part led to German Chancellor Angela Merkel's telephone call yesterday with Putin, urging him to use his influence with the rebels to ensure an urgent ceasefire.

"Moscow may have a last chance now to show that it really is seriously interested in a solution," Merkel's foreign minister, Frank-Walter Steinmeier told Bild am Sonntag newspaper.

"Now is the moment for everyone to stop and think to themselves what might happen if we don't stop the escalation."

Steinmeier's point is well made. During my time in eastern Ukraine there was always the sense that so long as the conflict was limited to Ukrainians fighting Ukrainians - even with Russian support - it would only generate "grave concern" in Europe and an expanding but manageable sanctions regime from the West.

But should the crash of MH17 prove unequivocally to have been the result of a missile attack by separatists with or without Russian involvement, it may well be a pivotal moment in redefining this six-month-old war. Meanwhile, with every day that passes and full access to the crash site consistently denied to international investigators the pressure on Moscow mounts.

Yesterday Dutch prime minister Mark Rutte, echoed global ultimatums to President Putin and the Kremlin.

"He has one last chance to show he means to help," said Rutte minutes after what he described as a "very intense" conversation with the Russian leader about bringing influence to bear on the separatists to allow rescuers to recover bodies at the crash site.

"I was shocked at the pictures of utterly disrespectful behaviour at this tragic spot," Rutte said, referring to allegations that bodies of the passengers, including 193 of his countrymen, were being dragged about and allowed to rot at the scene.

"I don't think it's too late. But with each passing day you lose a chance to protect and secure the scene and the bodies," said OSCE spokesman Michael Bociurkiw.

"It's a huge area. You need a lot of people to protect the bodies and give them the dignity they deserve."

Dutch Foreign Minister Frans Timmermans, expressing his government's frustration and that of other countries whose nationals were victims in the crash summed up the suspicions that continue over the separatists motives and intentions.

"There is a big difference between what the separatists say and what they do," he said, adding that the Netherlands would not rest until those responsible, and those that supported them, were brought to justice.

As yet more stories of personal grief unfolded, Malaysian Prime Minister Najib Razak revealed his own family was involved with his 83-year-old step-grandmother having been aboard the flight.

The United Nations too confirmed that 80 children were on board.

Yesterday, as the mourning and political wrangling over the tragedy reached a new level, the fighting on the ground continued around eastern Ukraine's two biggest cities, Donetsk and Luhansk.

A few months ago when my plane landed in Donetsk the region was only just moving into the full scale war that now engulfs it. For those ordinary Ukrainians I met and the loved ones of those killed aboard flight MH17, many difficult days still lie ahead.