The importance of language in the escalating crisis in Ukraine came to the fore when Russian President Vladimir Putin justified deploying troops in Crimea by saying Moscow needed to protect Russian-speakers there.

Traditionally, the west of the country as well as the capital Kiev has been Ukrainian-speaking, while the east and south -- closer to Russia and including the explosive peninsula of Crimea -- speak Russian.

Russia has refused to budge from its seemingly imminent annexation of Crimea, defying Western pressure at the U.N. Security Council, as Ukraine's ousted president prepared to make his first public appearance in more than a week Tuesday.

As Kremlin-backed forces tightened their grip on Crimea, Russia rebuffed pressure from Western members of the Security Council on Monday to change course on a secession referendum in the strategic peninsula.

An official of Russia's state atomic energy agency is to visit Iran on Tuesday for talks on building a second nuclear power plant, Iranian media reported.

Russia built Iran's sole existing nuclear power plant in the Gulf port of Bushehr and handed it over to Iranian engineers last September.

U.S. President Barack Obama spoke late Sunday with Chinese President Xi Jinping about ways to peacefully resolve a tense crisis over control of Ukraine's Crimea region, the White House said.

"They affirmed their shared interest in reducing tensions and identifying a peaceful resolution to the dispute between Russia and Ukraine," the White House said in a statement released on Monday.

The ousted president of Ukraine, Viktor Yanukovych, is to speak in southern Russia on Tuesday in his first public statement in over a week, Russian news agencies reported.

"The statement will be made in Rostov-on-Don. The exact time and place will be announced later," the agencies cited an unnamed source in his entourage as saying Monday.

Pro-Russian activists attacked a pro-Kiev rally in Crimea with clubs and whips on Sunday as thousands took to the streets across Ukraine in rival demonstrations, escalating separatist tensions in the troubled ex-Soviet state.

Interim Prime Minister Arseniy Yatsenyuk vowed Ukraine would not cede "an inch" of its territory to Moscow after Russian forces and pro-Kremlin gunmen took over the Black Sea peninsula.

The Kiev authorities should block the presidential bid of the leader of Pravy Sektor, or Right Sector, movement, Dmytro Yarosh, the Russian foreign ministry's rights envoy said Sunday.

"The de facto authorities in Kiev and their Western protectors must close the road to power for the neo-fascist Yarosh and his supporters," foreign ministry rights envoy Konstantin Dolgov wrote on Twitter.

Standing in the shadow of a massive, grey former KGB building in a busy Vilnius street, Lithuanian pensioner Rimantas Gucas worries history could repeat itself if the West fails to stop Russia from absorbing Ukraine's Crimean peninsula.

As Lithuania marks 24 years since it broke free from the crumbling Soviet Union and a decade since it joined NATO, people here and in fellow Baltic states Estonia and Latvia are jittery over Russian moves in Crimea.

Sarah Palin offered unsolicited advice Saturday to President Barack Obama on containing Russian aggression, saying "the only thing that stops a bad guy with a nuke is a good guy with a nuke."

The Republican former vice presidential candidate used a predominantly crass tone throughout her appearance at the Conservative Political Action Conference.

Victims of Stalin's mass deportations in 1944, Crimea's Tatar Muslim minority look wearily on next week's referendum on joining Russia, which could well bring the crisis on the tense peninsula to new heights.

At the Great Mosque in Bakhchysaray, near the southern tip of the Black Sea region, the local Tatar representative Akhtem Chiygoz slams the March 16 vote as "illegal".