(Adds Kerry quotes)
* U.S. says missile system brought in from Russia
* Many bodies said to be stored on refrigerated train
* Rebel treatment of victims' remains "grotesque" -Kerry
* Ukraine says separatists hamper access to crash site
* Britain says Russia faces "pariah" status
By Anton Zverev and Peter Graff
HRABOVE, Ukraine, July 20 (Reuters) - U.S. Secretary of State John Kerry laid out on Sunday what he called overwhelming evidence of Russian complicity in the downing of Malaysia Airlines flight MH17 and called rebels' behaviour "grotesque".
Kerry expressed horror at how pro-Moscow separatists at the crash sites in eastern Ukraine treated the remains of victims from Thursday's disaster, criticised Russian President Vladimir Putin, and threatened "additional steps" against Moscow.
"Drunken separatists have been piling bodies into trucks and removing them from the site," Kerry said on NBC television. "What's happening is really grotesque and it is contrary to everything President Putin and Russia said they would do."
British Foreign Secretary Philip Hammond echoed the criticism, urging Moscow to ensure international investigators had access to the crash sites. "Russia risks becoming a pariah state if it does not behave properly," he told Sky television.
At the biggest crash site, where emergency workers had bagged dozens of bodies on Saturday, all had been removed on Sunday morning. Bloodstained military stretchers that had carried them lay empty by the road, and rescue workers used a crane to move wreckage to reach human remains trapped beneath.
As Ukraine accused the rebels of hiding evidence relating to the shooting down of the airliner with the loss of 298 lives, a pro-Russian separatist leader said items thought to be the stricken Boeing's "black boxes" were now in rebel hands.
With Western anger rising at the apparently disrespectful treatment of the bodies by the rebels controlling the widely spread crash sites, nearly 200 corpses were taken to be stored on a refrigerated train at Torez, 15 km (9 miles) away.
"It's corpses. They brought the bodies overnight," a duty officer at the town's station told Reuters.
Officials from the Organization of Security and Cooperation in Europe (OSCE) were able to inspect some railway wagons.
Moscow denies any involvement in shooting down the airliner and has blamed the Ukrainian military. While stopping short of direct blame on Moscow, Kerry put forward the most detailed U.S. accusations so far that Russia provided the insurgents with the sophisticated anti-aircraft systems used to down the aircraft.
The United States had seen supplies moving into Ukraine from Russia in the last month, including a 150-vehicle convoy of armoured personnel carriers, tanks and rocket launchers given to the separatists, he said.
It had also had intercepted conversations about the transfer to separatists of the Russian radar-guided SA-11 missile system which it blames for the Boeing 777's destruction. "It's pretty clear that this is a system that was transferred from Russia," Kerry said in an interview on CNN.
"There's enormous amount of evidence, even more evidence that I just documented, that points to the involvement of Russia in providing these systems, training the people on them," Kerry said on CBS.
The disaster has sharply deepened the Ukrainian crisis in which the separatists in the Russian-speaking east have been fighting government forces since protesters in Kiev forced out a pro-Moscow president and Russia annexed Crimea in March.
The United States has already imposed sanctions on individuals and businesses close to Putin but Kerry indicated that President Barack Obama might go further. "The president is prepared to take additional steps," he told Fox News, although he ruled out sending in U.S. troops.
European Union ministers should be ready to announce a fresh round of sanctions at a meeting of the EU's Foreign Affairs Council this week, said a statement from British Prime Minister David Cameron's office, issued after telephone calls with French President Francois Hollande and German Chancellor Angela Merkel.
"They ... agreed that the EU must reconsider its approach to Russia and that foreign ministers should be ready to impose further sanctions on Russia when they meet on Tuesday," it said.
The leaders also agreed to press Putin to ensure investigators had free access to the crash site.
While Ukrainian President Petro Poroshenko issued a renewed appeal for backing from the international community, some European nations, with an eye to their trade links with Russia, have been less enthusiastic about confronting Moscow.
Kerry challenged the Europeans to be more assertive. "It would help enormously if some countries in Europe that have been a little reluctant to move would now recognise this wakeup call and join the United States and President Obama in taking the lead, and also stepping up," he said.
The United Nations Security Council was considering a draft resolution to condemn the attack, demand armed groups allow access to the crash sites and call on states in the region to cooperate with an international investigation. It could be put to a vote as early as Monday.
The Netherlands, whose citizens made up two-thirds of the 298 on the flight from Amsterdam to Kuala Lumpur, said it was "furious" about the manhandling of corpses strewn over open country and asked Ukraine for help to bring "our people" home.
A spokesman for Ukraine's Security Council, Andriy Lysenko, accused the rebels of a cover-up. "The terrorists are doing everything to hide the evidence of the involvement of Russian missiles in the shooting down of that airliner," he told a news conference in Kiev.
He said the rebels had taken debris and bodies from the crash site in trucks, tampering with a scene that investigators need to be secure to have a chance of determining what and who caused the plane to plunge into the steppe.
A separatist leader said items thought to be the "black box" voice and data recorders from the airliner had been found.
"They are under our control," Aleksander Borodai, prime minister of the self-styled Donetsk People's Republic, told a news conference.
OSCE observers visited part of the crash site for a third day on Sunday. Just before their arrival, emergency workers found parts of three more bodies and put them in black body bags on the side of a road.
At the site where the cockpit fell, in a field of sunflowers near the village of Razsypnoye, residents had made a small memorial shrine of flowers, candles in tiny jars and brightly coloured teddy bears.
Photocopied pictures of children and families killed in the disaster, apparently from news coverage of the victims, had been set out on the grass.
All bodies, including that of a woman who had lain naked under a tarp about 50 metres away, had been removed.
"There were five or six over here, and two or three over there," said a young man with a rifle guarding the site, who declined to give his name. "They took the bodies away to the morgue. Firstly, they were decomposing. And secondly, the smell was horrible."
In the Netherlands, prayers were said for the dead. Priests lit a candle for each of the 298 victims at St Bavo's Cathedral in Haarlem.
Fighting, meanwhile, continued. Ukrainian positions were fired on twice from across the border with Russia overnight, the Ukrainian armed forces said on Sunday. (Additional reporting by Pavel Polityuk, Natalia Zinets and Elizabeth Piper in Kiev, Jim Loney, Doina Chiacu, Ayesha Rascoe in Washington, William James in London and Nicholas Vinocur in Paris; Writing by Giles Elgood and David Stamp; Editing by Tom Heneghan)