NATO Secretary General Anders Fogh Rasmussen on Sunday praised Ukraine's army for staying out of the political crisis rocking the "close partner" of the Western alliance.

"I commend the statement of the Ukrainian army that it will in no way intervene in the political crisis," Rasmussen said in a statement following the ouster of president Viktor Yanukovych.

"It is important that this continues to be the case," he stressed.

"I continue to call for calm and restraint, so that all sides can focus on pursuing the path of democracy, stability and prosperity through peaceful dialogue and early elections."

Ukraine's army on Saturday ruled out any involvement in the country's unfolding crisis, after the police pledged support to the people following deadly violence in anti-government protests.

"Ukraine is a close partner to NATO and NATO is a friend of the Ukrainian people," Rasmussen said. "We look forward to continue cooperation with Ukraine based on the NATO-Ukraine Charter," established after the end of the Cold War.

A new era dawned in Ukraine on Sunday as parliament appointed a pro-Western interim leader after impeaching a defiant Yanukovych, whose whereabouts remained a mystery following a week of carnage.

But the future of the ex-Soviet state still hangs in the balance with its people split between a pro-Russian east and a nationalist, Ukrainian-speaking west pushing for closer ties with Europe.