The U.S. State Department sought the propaganda edge Wednesday evoking writer Dostoyevsky to denounce what it called Russian President Vladimir Putin's "fiction: 10 false claims about Ukraine."

In a mounting war of words between the former Cold War foes, U.S. and Russian officials have in recent days put out starkly different versions surrounding the deployment of Russian troops in Ukraine's Crimea peninsula.

Former U.S. secretary of state Hillary Clinton has compared Russian President Vladimir Putin's recent steps in Ukraine to aggression by Adolf Hitler in 1930s Nazi Germany, a local paper reported.

Clinton, speaking at a private event Tuesday in southern California, said Putin's apparent deployment of Russian troops into neighboring Ukraine -- a former Soviet satellite state -- to protect Russian citizens and Russian-speakers recalls moves by Hitler to protect ethnic Germans living outside of Germany.

Russian President Vladimir Putin has calmed fears of an imminent war between Russia and Ukraine's new authorities but also made clear that Moscow has no intention of loosening its new grip on Crimea in defiance of Western anger.

Breaking an uncharacteristic silence since the downfall of president Viktor Yanukovych 10 days ago, Putin on Tuesday displayed no fear of a prolonged crisis in ties with the West over the situation in the Ukrainian region of Crimea which is now controlled by pro-Moscow forces.

President Vladimir Putin denied on Tuesday that Russian troops were operating in the Ukrainian Black Sea region of Crimea, while sending Moscow's forces to Ukraine would be an entirely legitimate move but also a last resort.

U.S. President Barack Obama, however, said Putin's rationale for his incursion into Crimea was not "fooling anybody" and said Russian "meddling" would push states away from Moscow.

Russian President Vladimir Putin on Tuesday told troops to return to their permanent bases after calling a snap drill to check their battle-readiness last week.

"The commander-in-chief President Vladimir Putin gave the order to the troops and units taking part in military exercises to return to their permanent bases," Putin's spokesman Dmitry Peskov told Russian news agencies.

Ukraine's deposed president Viktor Yanukovych is still the legitimate head of state of the country even if his authority is "negligible", Russian Prime Minister Dmitry Medvedev said Monday.

Medvedev added that Russia does not recognize the new authorities who took power in Kiev after the overthrow of Yanukovych, saying they had violated the constitution.

Russia's Vladimir Putin has agreed to a proposal from Angela Merkel to set up a contact group on Ukraine, the German government said Sunday.

The German chancellor put the proposal to Putin in a telephone conversation late Sunday in which she also "accused the Russian president of violating international law with the unacceptable Russian intervention in Crimea," said a government statement.

U.S. Secretary of State John Kerry bluntly warned Russia Sunday that it risked losing its seat among the prestigious Group of Eight nations, as well as economic turmoil and sanctions, over the Ukraine crisis.

The top U.S. diplomat hit the Sunday talk shows to ratchet up pressure on Moscow, after he convened a crisis conference call with European and Canadian foreign ministers and President Barack Obama held a 90-minute phone call with Russian counterpart Vladimir Putin Saturday.

British Foreign Secretary William Hague has urged his Russian counterpart to de-escalate the situation in Ukraine's restive Crimea peninsula, ahead of a trip to Kiev on Sunday.

"Have spoken to Foreign Minister (Sergei) Lavrov to call for de-escalation in Crimea and respect for sovereignty and independence of Ukraine," Hague said in a Twitter message on Saturday.

Russian President Vladimir Putin on Friday called for a rapid return to normality in Ukraine and warned against any further escalation of unrest, in telephone calls with key EU leaders, the Kremlin said.

Putin emphasized "the extreme importance of not allowing a further escalation of violence and the necessity of a rapid normalization of the situation," the Kremlin said after Putin had separate phone calls with British premier David Cameron, German Chancellor Angela Merkel and European Union president Herman van Rompuy.