US President Barack Obama has hit out at Moscow’s expansionism as a “sign of weakness” after Russia took control of the Crimean peninsula from Ukraine, fuelling fears of more intervention in the region.

“Russia is a regional power that is threatening some of its immediate neighbours, not out of strength but out of weakness,” Obama told journalists after a nuclear security summit in The Hague.

Obama said that while the US also had influence over its neighbours, “we generally don’t need to invade them in order to have a strong co-operative relationship with them”.

The Crimean crisis has sparked the most explosive East-West confrontation since the Cold War era.

“The fact that Russia felt (the need) to go in militarily and lay bare these violations of international law indicates less influence, not more,” Obama said, rejecting Putin’s claim that Russian speakers had been threatened in Crimea and in Ukraine.

“There has been no evidence that Russian speakers have been in any way threatened,” the US president said, the day after a Group of Seven (G7) summit suspended Russia from the grouping of rich nations.

“I think it is important for everybody to be clear and strip away some of the possible excuses for potential Russian action,” he said.

Ukraine’s parliament on Tuesday sacked the crisis-hit country’s defence minister, after his forces undertook a humiliating withdrawal from Crimea without firing a shot against Russian forces who claimed the Black Sea peninsula.

Ukraine’s ground commanders in Crimea had complained bitterly of confusion among the top brass in Kiev since Putin’s decision on March 1 to seek the right to use force against his neighbour in response to last month’s fall in Kiev of a pro-Kremlin regime.

Tensions between the two neighbours seemed ready to spike further when Russian television aired what it claimed was a tape of former Ukrainian premier Yulia Tymoshenko – an opposition leader released from jail after the pro-Kremlin regime’s fall – urging the “wiping out” of Russians over the seizure of Crimea.

Tymoshenko admitted that her voice was on the tape but insisted that her comments had been manipulated.

Obama’s G7 summit in The Hague agreed on Monday to deepen Moscow’s isolation and meet on its own – without Russia – in Brussels instead of gathering in Sochi in June.

But the Kremlin shrugged off the seven world leaders’ decision as “counter-productive” but otherwise harmless.