Washington, April 17 (IANS): US President Barack Obama once again warned Russia against further destabilizing Ukraine.

Obama said Wednesday that it was "absolutely clear" that Russia had violated Ukraine's sovereignty and territorial integrity by annexing Crimea last month and was continuing to do so by supporting "non-state militias" in eastern Ukraine, Xinhua reported.

"What I've said consistently is that each time Russia takes these kinds of steps, that are designed to destabilise Ukraine and violate their sovereignty, that there are going to be consequences," Obama added.

Washington has targeted a number of key Russian and Crimean officials as well as a Russian bank following Moscow's move on Crimea.

Obama signed an executive order in March authorizing expanded sanctions against more individuals and entities as well as key sectors of Russia's economy including energy, banking, mining and defence.

The Ukrainian government Monday night launched military operations to flush out pro-Russian militants occupying government buildings in the eastern part of the country, leaving at least four people dead.

"The sharp escalation of the conflict" had placed Ukraine "in effect on the verge of civil war," Russian President Vladimir Putin told German Chancellor Angela Merkel.

Moscow has rejected accusations that Russia was destabilizing Ukraine.