Dutch forensic experts on Monday were examining bodies from the MH17 plane disaster being held at an east Ukraine train station as Kiev and insurgents wrangled over the fate of the remains.
As world leaders deplored the "shambolic" state of the crash site left in the hands of the rebels and accused Russia of supplying the weapons allegedly used to shoot down the passenger jet, Moscow hit back and sought to shift the blame to Kiev.
On the ground, the animosity between Ukraine's warring sides was underlined by intense shelling rained down in the rebel stronghold Donetsk, a city just 60 kilometres (about 40 miles) from the station where the bodies are being held in refrigerated wagons.
Four people were killed and terrified civilians fled, as Ukraine President Petro Poroshenko quickly ordered his troops to hold fire within a 40-kilometre radius around the crash site, where forensic experts were heading.
Russian President Vladimir Putin, the target of global ire for failing to use his influence to rein in the pro-Russian rebels, appeared to adopt a concilatory tone Sunday, saying Moscow would do "everything in its power" to resolve the three-month-old Ukrainian conflict.
But on Monday, Moscow moved to slap down accusations by US Secretary of State John Kerry who had said the missile system used to shoot down the aircraft was transferred from Russia to separatists.
A senior Russian defence ministry official insisted that "Russia did not give the rebels Buk missile systems or any other kinds of weapons or military hardware".
Instead Moscow challenged Kiev, saying records show a Ukrainian military plane was flying just three to five kilometres from the Boeing 777 before it went down on Thursday, killing all 298 people on board.
"With what aim was a military plane flying along a civilian aviation route practically at the same time and at the same flight level as a passenger liner?" asked Lieutenant-General Andrei Kartopolov.
Moscow's riposte came after Kiev released fresh recordings of what it says are intercepted conversations between rebels conspiring to hide the flight's black boxes from international monitors.
And the US embassy confirmed as authentic recordings released earlier by Kiev of an intercepted call between an insurgent commander and a Russian intelligence officer as they realised they had shot down a passenger jet.
The Washington Post said Ukraine's counterintelligence chief had photographs and other evidence that three Buk M-1 anti-aircraft missile systems moved from rebel-held territory into Russia less than 12 hours after the crash.
- Civilians flee Donetsk fighting -
At the Torez railway station, an overpowering stench filled the air as Dutch investigators, wearing masks and headlights, opened each of the train wagons holding the remains of over 200 recovered bodies.
"I think the storage of the bodies is (of) good quality," Peter Van Vliet, the forensic expert leading the Dutch team.
"Now we hope that the train will leave so that we can do the necessary analyses. It is not technically possible here," he said, as 50 armed insurgents looked on.
Kiev said the remains of the victims should be transferred to the Netherlands and has accused rebels of refusing to release the grisly cargo.
Insurgents say however that Kiev could not be trusted and that they would only give control over the remains to international experts.
As grief turned to anger, the Dutch public prosecutor's office said it had opened a criminal probe into the downing of the plane, which had 193 Dutch on board.
In Donetsk, insurgent fighters closed off the roads around the airport and train station on the edge of the city as local residents escaped intense shelling in minibuses and on foot.
A rebel fighter told AFP that government troops had attacked their positions near the transport hub at around 10 am (0700 GMT).
- Crash site 'shambolic' -
"They came within about two kilometres of the station," insurgent gunman Volodya told AFP.
Four days after the crash, patience was wearing thin over the limited access to the crash site in Grabove, where debris is spread over kilometres and where salvage workers were still combing the vast cornfields for remains of the victims.
"As anyone who has been watching the footage will know, this is still an absolutely shambolic situation," Australian Prime Minister Tony Abbott said.
Malaysia has also expressed concerns that "the sanctity of the crash site has been severely compromised".
Kerry has slammed as "grotesque" the manner in which "drunken separatist soldiers" were allegedly "unceremoniously piling bodies into trucks, removing both bodies, as well as evidence, from the site".
Insurgents however said they had moved scores of bodies "out of respect for the families".
But that is little comfort for outraged families of the victims.
The anger was palpable in an open letter from Dutch national Hans de Borst, who lost his 17-year-old daughter Elsemiek.
"Thank you very much Mr Putin, separatist leaders or the Ukrainian government, for murdering my dear and only child," he wrote in the letter published by Dutch media.
"I hope that you're proud to have destroyed her young life and that you can look yourself in the mirror."
- Fresh sanctions? -
The UN Security Council is expected to adopt an Australia-backed resolution demanding pro-Russian separatists grant unrestricted access to the crash site to international experts when it meets at 1900 GMT.
European leaders have signalled they could ramp up sanctions against Russia as early as Tuesday -- barely a week after the last round of toughened embargoes.
Whole sectors of the economy including goods with possible military uses could be targeted, British Prime Minister David Cameron said.
The separatists' violent bid to join Russia is the latest chapter in a prolonged crisis sparked by Kiev's desire for closer ties with the EU -- a sentiment many in the Russian-speaking east do not share.