Ukraine launched a military assault on Monday to break pro-Russian rebels' hold on the eastern city of Donetsk in the first major hostilities in the area since Malaysia Airlines Flight MH17 was shot down last week.
As Dutch investigators arrived to inspect the bodies of hundreds of victims near the crash site, the fighting in Donetsk served as a reminder of the dangers they face working in a war zone.
Artillery fire sent plumes of smoke skyward near the Donetsk railway station, about 40 miles from the crash site, in what the separatists said was an attempt by government forces to enter the city, which they seized in April.
Sergei Kavtaradze of the rebels' self-proclaimed Donetsk People's Republic said at least four army tanks and armored vehicles were trying to break through into the city.
A Ukrainian military spokesman confirmed that the operation was in progress but would not comment on reports of troops entering Donetsk. "The active phase of the anti-terrorist operation is continuing. We are not about to announce any troop movements," said Vladyslav Seleznyov.
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.
Against a background of international horror over the fate of the remains of the 298 victims of the Malaysia Airlines disaster, the first international investigators reached eastern Ukraine on Monday.
Three members of a Dutch disaster victim identification team arrived at a railway station near the crash site where rebels say 247 bodies have been stored in refrigerated wagons. More than half of the crash victims were Dutch.
The head of the team inspected the storage of the bodies in the rail cars and, despite an overwhelming stench of decomposition when the doors were opened, said it was fine.
"The storage of the bodies is of good quality," said Peter van Vliet, whose team went through the wagons dressed in surgical masks and rubber gloves.
He said he had been told the train would be leaving the station at Torez later on Monday so the bodies can be taken where they can be identified and eventually repatriated. He could not say where it was going.
Ukrainian officials said that as of Monday morning, 272 bodies and 66 fragments of bodies had been found.
Michael Bociurkiw, a spokesman for the Organization for Security and Cooperation in Europe, said reports from the group's investigators in Ukraine suggest some bodies were incinerated without a trace.
"We're looking at the field where the engines have come down. This was the area which was exposed to the most intense heat. We do not see any bodies here. It appears that some have been vaporized," he said from the crash site.
The Netherlands and Russia agreed Monday that the International Civil Aviation Organization should lead the investigation.
But Dutch Prime Minister Mark Rutte also said Monday that Russian President Vladimir Putin needed to do more to convince the separatists to lay down their arms and allow investigators unfettered access to the crash site.
“It is clear that Russia must use her influence on the separatists to improve the situation on the ground,” he told the Dutch parliament. “If in the coming days access to the disaster area remains inadequate, then all political, economic and financial options are on the table against those who are directly or indirectly responsible for that.”
The shooting down of the airliner on Thursday has sharply deepened the Ukrainian crisis, in which separatists in the mostly Russian-speaking east have been fighting government forces since protesters in Kiev forced out a pro-Moscow president in February and Russia annexed Crimea in March.
Putin, in a televised address Monday, echoed Rutte's call for separatists to allow international experts access to the crash site but reiterated his line that the downing of the airliner must not be used for political ends.
The United States and its allies have already pointed fingers at the pro-Russian rebels and at Moscow over the downing of the plane, citing signals intelligence that shows the missile that shot down MH17 was fired from rebel-held territory.
U.S. Secretary of State John Kerry over the weekend laid out what he called overwhelming evidence of Russian complicity in the shooting and expressed disgust at how the bodies of the victims had been treated at the crash site.
"Drunken separatists have been piling bodies into trucks and removing them from the site," he said on NBC television on Sunday. "What's happening is really grotesque, and it is contrary to everything President Putin and Russia said they would do."
Television images of the rebel-controlled crash sites, where the remains of victims lay 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 he had spoken to Putin for the first time about the disaster. At least 27 Australians were on the flight from Amsterdam to Kuala Lumpur.
Abbott said an Australian investigation team was in Kiev but was unable to travel to the site. He said there was 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."
Pro-Moscow rebels piled nearly 200 bodies from the downed Malaysian jetliner into four refrigerated boxcars Sunday in eastern Ukraine, and cranes at the crash scene moved big chunks of the Boeing 777, drawing condemnation that the site was being tampered with.
The United Nations Security Council is scheduled to vote on Monday on a resolution that would condemn the downing of the plane, demand that those responsible be held accountable and that armed groups not compromise the integrity of the crash site.
EU foreign ministers are due to meet on Tuesday and could announce more sanctions against Moscow. Britain is pushing for tougher measures, and Italy said it expected a "strong and unified response.”
Ukraine said it was willing to hand over coordination of the crash investigation to international partners, perhaps led by the Netherlands, but Kiev was convinced the plane was shot down by "professionals."
"At the moment, we have no doubt that the plane was shot down. The reason for it — a missile strike most likely from a BUK-M1," Prime Minister Arseny Yatseniuk told a news conference. "It is clear that this system could not be operated by drunk pro-Russian terrorists. There were professional people."
Kerry said the United States has seen supplies moving into Ukraine from Russia in the last month, including a 150-vehicle convoy of armored personnel carriers, tanks and rocket launchers given to the separatists.
The U.S. also intercepted conversations about the transfer to separatists of a Russian radar-guided BUK missile system, which it blames for the Boeing 777's destruction.
Russia's Defense Ministry addressed that allegation Monday, denying that it ever delivered any such missile systems — "or any other weapons" — to the separatists in Ukraine.