"Putin = Dracula," "Putin = Hitler," "Putin, get out": posters and caricatures attacking the Russian leader have multiplied over the last couple of weeks on the Maidan, Kiev's protest tent-city.

As Russian forces have taken control of Ukraine's Crimean peninsula, protesters have reveled in making comparisons between Russian President Vladimir Putin and Adolf Hitler, combining their names in slogans that conclude that "Putler has gone mad."

The European Parliament on Thursday backed tough new sanctions against Russia, including an arms embargo and asset freezes, unless Moscow reverses its military intervention Crimea.

Lawmakers passed a non-binding resolution calling for the European Union to consider "appropriate measures," such as an embargo on arms and technologies that could be used for military operations.

Washington warned Russia on Thursday it was preparing a "very serious" response together with Europe to a breakaway vote in Ukraine's Crimea that has sparked the most explosive East-West standoff since the Cold War, as Kiev said it was still possible to resolve the crisis with Russia peacefully.

U.S. Secretary of State John Kerry said Russia needed to show immediate flexibility over the Black Sea peninsula's Sunday referendum on switching over to Kremlin rule -- a vote backed by Moscow but not recognized by Kiev or much of the international community.

Ukraine moved Thursday to mobilize a volunteer force to ward off Russia's expansionist threat as Berlin warned Moscow of long-term damage to its economy and EU relations over the Crimea crisis.

The Verkhovna Rada parliament unanimously backed the creation of a new force of up to 60,000 volunteers who could keep Russian troops from advancing beyond the Crimean peninsula they seized at the start of the month.

A senior Russian lawmaker said military units are occupying positions in Crimea in case of armed attack from Kiev, in the first apparent admission by Moscow that its forces have occupied the Ukrainian region in a military operation.

President Vladimir Putin has insisted that the uniformed gunmen who are openly patrolling Crimea with military hardware and weapons are local self-defense brigades and even suggested they bought their uniforms in a shop.

The United States, with its abundant supplies of natural gas, would seem to have an easy answer to Europe's fears that a strong response to Russia's rapid takeover of Ukraine's Crimea region could prompt Vladimir Putin to shut down gas lines that keep European homes warm, factories humming and electricity flowing.

Trouble is: Right now there's no way to get meaningful American supplies across the Atlantic Ocean.

Russia would be unable to disrupt the U.S. military's withdrawal from Afghanistan even if it cut off access to supply routes across its territory, a top U.S. commander said Wednesday.

Amid rising tensions between Washington and Moscow over the crisis in Ukraine, the head of NATO-led forces in Afghanistan reassured lawmakers that Russia could not hold up a planned troop drawdown there.

The White House's top arms control official on Wednesday said U.S. cooperation with Russia on agreements limiting nuclear arsenals would survive the worst East-West tensions in years sparked by Ukraine.

Elizabeth Sherwood-Randall said that U.S. and Russian officials were even now working "effectively" together to prepare for a nuclear security summit in The Hague later this month which President Barack Obama will attend.

The East-West split re-opened by the crisis in Ukraine hardened Wednesday when President Barack Obama threw Washington's weight firmly behind Ukraine in its stand-off with Moscow.

Obama welcomed Kiev's interim premier Arseniy Yatsenyuk to the White House and stood by his side as both leaders sternly warned Russia that Ukraine would not surrender its sovereignty.

U.N. chief Ban Ki-moon appealed to the United States and Russia Wednesday to "re-energize" talks aimed at resolving the bloody civil war in Syria as it enters its fourth year.

The U.N.-led peace talks, dubbed Geneva II, broke down on February 15 when a second round ended with no new date set for them to reconvene.