Punitive sanctions and the calling into question of a key arms control treaty with Washington have ratcheted up pressure on Russia, leaving President Vladimir Putin few palatable options to resolve the crisis in Ukraine, analysts say.

Putin might have thought he could get away with keeping the conflict simmering with a divided Europe wary of imposing tough sanctions that could plunge its own economy back into recession.

Australian Prime Minister Tony Abbott Saturday welcomed the recovery of more remains from the crash site of Flight MH17 but said it would take at least another week to complete the task.

NATO must rethink its long-term relationship with Russia and strengthen the alliance's ability to respond quickly to any threat, British Prime Minister David Cameron said Saturday.

Russian President Vladimir Putin and his U.S. counterpart Barack Obama agreed during a phone call on Friday the current standoff in Ukraine was not in the interest of their countries, the Kremlin said.

"The presidents agreed that the current situation is not in the interests of either country," said a Kremlin statement.

The U.S. Senate approved President Barack Obama's nominee for ambassador to Moscow Thursday, a quick confirmation amid a long backlog of would-be envoys awaiting a vote.

Fourteen people were killed, including at least 10 government soldiers, in fighting overnight close to the crash site of downed Malaysia Airlines flight MH17, a Ukrainian military spokesman said Friday.

"In total it is known that 14 people died but the bodies of four of them have not been identified and could be Ukrainian soldiers or terrorists," said Oleksiy Dmytrashkivsky.

Kiev on Thursday announced a day-long halt to its deadly offensive to oust pro-Russian rebels in east Ukraine after fighting had stalled efforts by international investigators to kickstart a probe into the downing of Malaysia Airlines flight MH17.

International fallout from the crisis tearing apart the ex-Soviet nation rumbled on as the Group of Seven major developed economies warned Moscow that it could face even tougher sanctions over its backing for the insurgents, despite the EU and U.S. already hitting Russia with the most punitive measures since the Cold War.

A British judge said Thursday that the Russian state has a case to answer in the radioactive poisoning of Alexander Litvinenko as he formally opened a public inquiry into the death of the former spy.

Judge Robert Owen said he would be able to hear secret evidence behind closed doors about the 2006 murder of Litvinenko, who accused President Vladimir Putin from his deathbed of being linked to his killing.

The European Union formally adopted broad economic sanctions against Russia on Thursday, aiming to make it pay a price over the Ukraine crisis in the hope Moscow will reverse course.

They were published in the EU's Official Journal later in the day, meaning that they come into effect on Friday.

Russia has asked Bulgaria to extradite a prominent opponent of Russian President Vladimir Putin who was arrested at Sofia airport, the Bulgarian prosecution announced on Thursday.

Nikolay Koblyakov, founder of the French non-governmental organisation Russie-Liberte which had staged a series of anti-Putin actions in France, was detained on an Interpol warrant at Sofia airport on Tuesday and held for 72 hours, the interior ministry said.