The White House on Thursday reinforced U.S. warnings to Russia that it must avoid "miscalculations" in military drills along the border of troubled Ukraine.

The comments, which built upon statements by U.S. Defense Secretary Chuck Hagel, appeared to reflect Washington's concern that Russian maneuvers near the ex-Soviet state could trigger events which may get out of control.

Russia had little option other than to offer sanctuary to deposed Ukrainian president Viktor Yanukovych, even if there is little love lost between him and President Vladimir Putin, analysts said Thursday.

Yanukovych is now widely believed to be in Russia after he released a statement saying he had asked Moscow to ensure his security and sources in the country said his wish had been satisfied on "Russian territory."

The United States on Thursday denounced what it said was the growing use of security forces by repressive regimes to crackdown on a worldwide groundswell of pro-democracy protests.

"The fundamental struggle for dignity, for decency in the treatment of human beings... is a driving force in all of human history," Secretary of State John Kerry said as he released his department's 2013 human rights report.

Lawmakers in Crimea's regional parliament, which is currently being controlled by pro-Russian gunmen, voted Thursday to hold a referendum on May 25 on the region's status in Ukraine, the parliament's press service said.

Legislators fixed the vote to determine whether to increase Crimea's autonomy from Kiev and they also voted to dismiss the region's current government, which has backed the new interim authorities in the capital.

Switzerland said Thursday it was prepared to freeze any funds Ukraine's ousted president Viktor Yanukovych might have in Swiss banks.

The Swiss government has decided "in principle to freeze any possible funds Mr Yanukovych may have in Switzerland", foreign ministry spokesman Pierre-Alain Eltschinger told Agence France Presse in an email.

Anxious Western powers voiced fear over the growing Crimea crisis Thursday, warning Russia not to escalate tensions and telling pro-Moscow separatists they were playing a "dangerous game."

After dozens of pro-Russian gunmen seized government buildings in the volatile peninsula -- raising fears of a full-blown regional conflict -- NATO leader Anders Fogh Rasmussen tweeted his concern and pleaded with Moscow "not to take any action that can escalate tension or create misunderstanding."

Here is a snapshot of recent events in Ukraine, where authorities warned Moscow on Thursday not to intervene after pro-Russian gunmen seized government buildings in the Crimean region.

FEBRUARY 18: Violence erupts as 20,000 pro-European protesters march from Kiev's Independence Square to demand that president Viktor Yanukovych be stripped of key powers.

Mounting separatist tensions in Ukraine's Russian-speaking Crimea peninsula have reached dangerous levels and could lead to fresh domestic turmoil or even spark an outright invasion by giant neighbor Russia, analysts say.

On Thursday, pro-Moscow gunmen seized control of the parliament and government headquarters in the regional capital Simferopol, sparking warnings from Ukraine's interim leader that any troop movements at Russia's Black Sea fleet -- based in Crimea -- would be seen as "military aggression".

Ukraine's parliament on Thursday approved the nomination of pro-EU Arseniy Yatsenyuk as the crisis-hit country's new prime minister until presidential polls are held in May.

Yatsenyuk was one of the most prominent leaders of the three-month anti-government protests that swept Ukraine, culminating in deadly violence last week that precipitated the ouster of president Viktor Yanukovych and the collapse of his entire government.

Dozens of pro-Russian gunmen in combat fatigues seized parliament and government buildings on Ukraine's volatile Crimea peninsula Thursday as the country's ousted leader won assurances that Moscow would protect him.

The dawn raid in Crimea came a day after Russian President Vladimir Putin ordered snap combat readiness drills to be held near the Ukrainian border, raising fears the Kremlin might use force to sway the outcome of a three-month crisis that has pitted Moscow against the West in a Cold War-style confrontation.