Ukraine has "compelling evidence" Russia played a defining role in the shooting down of a Malaysian airliner by providing the rebels with missile systems and a crew, the country's counter intelligence chief said on Saturday.

Vitaly Naida said Kiev had proof three BUK-1, or SA-11 radar guided missile systems, had entered Ukraine from neighbouring Russia along with a three-man crew.

"We have compelling evidence that this terrorist act was committed with the help of the Russian Federation. We know clearly that the crew of this system were Russian citizens," he told a news conference.

Calling on Russia to give Ukraine the names and surnames of the crew so that Kiev could question them, he said the three systems had now been moved back to Russia, showing journalists pictures of the missile systems in various locations.

"We know about the three people who came together with these systems from the territory of Russia," he said.

Earlier, Ukraine accused Russia and pro-Moscow rebels of destroying evidence of "international crimes" from the wreckage of the Malaysian airliner.

Fighting and artillery barrages flared near the Russian border in the hours after President Barack Obama called the loss of flight MH17 a "wake-up call" to Europe to join the US in threatening Moscow with heavier economic sanctions if it does not use its influence to help end a conflict that has driven the gravest East-West confrontation since the Cold War.

Malaysia, whose national airline has been battered by its second major disaster this year, said it was "inhumane" to bar access to the site around the village of Hrabove, near the city of Donetsk, and said Russia was doing its "level best" to help. It defended the use of an air corridor over Ukraine's war zone.

"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.

At Hrabove, one armed man from the separatist forces told Reuters that bodies had been taken away in trucks. Amid reports of looting, militants and local people say they have been doing their best to collect evidence and preserve human remains.

As the stench of death begins to pervade the area, a Reuters correspondent watched rescue workers carry bodies across the fields and gather remains in black sacks. One local resident said Ukrainian fighter jets had flown over the area earlier.

THREATS

Quite who controls what around the site is unclear. Rebel forces, who have declared a Donetsk People's Republic in the Russian-speaking east and want union with Moscow, have set up cordons and checkpoints around the area.

The security council in Kiev said staff of the emergencies ministry had found 186 bodies - a little more than half the 298 aboard the Malaysia Airlines Boeing 777 - and had checked some 18 sq km of the scattered 25-sq.km crash site. But the workers were not free to conduct a normal investigation.

"The fighters 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."

He added that he had no information on the black box flight recorders, both of which separatists have said have been found.

A party of observers from Europe's OSCE security body, based in Donetsk, visited the site on Friday and found access limited by what it said were hostile armed men, some of them drunk.

Following a demand from the United Nations Security Council for an independent investigation, both sides in the conflict have offered ceasefires and cooperation but the situation on the ground remains confused and Ukrainian officials said there were several clashes overnight in areas near the city of Luhansk.

A team of Malaysian experts flew in to Kiev on Saturday.

Ukrainian Prime Minister Arseny Yatseniuk issued a statement after he spoke to the foreign minister of The Netherlands - more than half those aboard the flight from Amsterdam were Dutch.

He said government experts sent to the site "were not given the opportunity to collect evidence. They gave them less than an hour there, and made them leave the site of the catastrophe threatening to take them hostage."

Malaysian Transport Minister Liow Tiong Lai said on Saturday he would fly to the Ukraine capital of Kiev to ensure an investigating team gets safe access to the site. Before setting off, he said it would be "inhumane" not to have access, but said Moscow was trying to help: "They are trying their level best to assist Malaysia to ensure we have a safe site," Liow said.

Defence Minister and former transport minister Hishammuddin Hussein said a priority was to ensure debris was not tampered with.

"We want to get to the bottom of this," he added, saying that Malaysia had been in touch with officials in Russia, Ukraine, the United States, Britain and China.

"We do not have a position until the facts have been verified, whether the plane was really brought down, how it was brought down, who brought it down," he said.

International observers said gunmen stopped them examining the site properly when they got there on Friday. More than half of the victims were Dutch in what has become a pivotal incident in deteriorating relations between Russia and the West. - Reuters