The black boxes from the doomed Malaysia Airlines flight MH17 that came down in eastern Ukraine have arrived in Britain for expert analysis, the government said Wednesday.

The recorders have been delivered to the Air Accidents Investigation Branch headquarters in Farnborough, southwest of London.

Russia announced Wednesday that it had begun expanding and modernizing its Black Sea fleet based in Crimea with new ships and submarines, just months after annexing the peninsula from Ukraine.

"Today we have started forming a powerful Black Sea fleet with an absolutely different level of air service, coastal missile and artillery troops and marines," said Alexander Vitko, the Black Sea fleet commander, in a message to servicemen.

Malaysia's bitterly divided political forces put aside their differences on Wednesday to denounce the attack on flight MH17 as a heinous international crime and call jointly for swift justice for those responsible.

Prime Minister Najib Razak led the charge, condemning the Malaysia Airlines flight's shooting down by a surface-to-air missile.

Russia is struggling with a flood of refugees who already number half a million from the fighting in eastern Ukraine, and many appear increasingly likely to stay, officials and activists said. 

Britain is still exporting arms and military equipment to Russia, according to a parliamentary report released Wednesday just hours after Prime Minister David Cameron rapped France for selling weapons to Moscow.

The delivery of French Mistral-class warships to Russia would be "completely inappropriate" given the West's misgivings about Moscow's role in Ukraine, the United States said Tuesday.

"We don't think anyone should be providing arms to Russia," deputy State Department spokeswoman Marie Harf told reporters, adding U.S. officials had voiced their concern over the deal in recent days to French Foreign Minister Laurent Fabius.

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 NGOs on Tuesday vowed to appeal against being labelled as "foreign agents" under a law Western rights groups condemned as a "stranglehold" on freedom of expression.

The Russian justice ministry on Monday added five prominent non-governmental organizations to its register of "foreign agents," which requires them to mark all their paperwork accordingly and undergo stricter audits.