U.S. intelligence officials were expected to present data Tuesday backing up the theory that pro-Russian rebels were responsible for the downing of flight MH17 over eastern Ukraine.

The Malaysia Airlines Boeing 777 was blown out of the sky Thursday by what is believed to have been a surface-to-air missile, killing all 298 passengers and crew on board.

Kiev said Tuesday that it has launched a criminal investigation against Russian Defense Minister Sergei Shoigu and a shadowy Muscovite millionaire for organizing and financing "illegal armed groups" in Ukraine.

The investigation comes just over a month after Russia launched an investigation of its own against Ukraine's Interior Minister Arsen Avakov and a billionaire local governor over the killings of civilians and journalists in conflict-torn east Ukraine.

EU foreign ministers tackled tougher Ukraine crisis sanctions against Russia Tuesday, divided as to how far to go and with British-led calls for an arms embargo putting France on the spot.

The downing of Malaysian Airlines flight MH17 last week, allegedly by pro-Moscow rebels using Russian equipment, has changed the situation completely requiring a much tougher response, said Britain's Philip Hammond.

Russian President Vladimir Putin promised Tuesday to do everything possible to influence pro-Russian separatists in eastern Ukraine and help ensure a full probe into the Malaysia Airlines crash last week.

However he added that it would not be enough with Kiev's continuing military operation against the rebels, adding that the West must push Ukraine's authorities to declare a ceasefire.

Mortar blasts rocked the outskirts of rebel stronghold Donetsk Tuesday as Ukrainian soldiers clashed again with pro-Russian insurgents a day after five civilians were reported killed by shelling in the area.

Agence France Presse reporters heard artillery fire coming from the Ukrainian side in the village of Oktyabrsky close to the airport, which has now come under full government control.

The first bodies from the MH17 crash in Ukraine will be flown on Wednesday to the Netherlands, where their identification could take months, Prime Minister Mark Rutte said.

"Tomorrow the first plane (with bodies) will leave for Eindhoven," in the southern Netherlands, Rutte told journalists after the bodies arrived in Ukraine's Kharkiv from rebel-held territory.

Presidents from nine ex-communist NATO members met in Warsaw on Tuesday for talks on how to re-enforce the alliance's eastern frontier as if faces a resurgent Russia.

"The Russia-Ukraine conflict is Europe's most important security challenge since the end of the Cold War," Polish President Bronislaw Komorowski told reporters as the leaders met to forge their regional defense strategy ahead of a NATO summit in September.

The downing of the MH17 flight over rebel territory in Ukraine has put Moscow's support of the separatists under more scrutiny than ever amid allegations the plane was blasted out of the sky with a Russian-supplied missile system.

The US, whose relations with Moscow have dropped to a post-Cold War low over the Ukraine crisis, has led the charge.

The downing of flight MH17 over eastern Ukraine was a "hideous crime" and hurdles to a probe of the tragedy are an "outrage", global airline federation IATA said on Tuesday.

"The passengers and crew aboard the aircraft were the victims of a hideous crime. It was also an attack against the air transport system," said Tony Tyler, head of the International Air Transport Association.

Lithuania's President Dalia Grybauskaite said Tuesday the European Union was compromising its values to protect trade ties with Russia, pointing to a French warship agreement with Moscow.

"We see the Mistralisation of European policy," Grybauskaite said, referring to a 1.2 billion euro ($1.6 billion) deal to supply Russia with two French Mistral warships.