Russia has re-deployed "significant" military forces near its border with Ukraine and stockpiled additional tanks and artillery at a southwestern site, a U.S. official said Friday.

Washington had information that the equipment and forces were being prepared by Moscow "to provide active support for separatist fighters," a senior U.S. administration official said.

Russian investigators on Friday launched a criminal probe after a raid on the home of top opposition leader Alexei Navalny yielded an allegedly stolen artwork.

Navalny is currently under house arrest over unconnected fraud charges and allies say the latest police move is designed to ramp up pressure on the fierce Kremlin critic and his crusading anti-corruption organization.

Russian President Vladimir Putin and his U.S. counterpart Barack Obama will discuss the situation in Ukraine, Iraq and Syria "in the coming days," a top aide said on Friday.

Speaking to reporters, Putin's top foreign policy adviser, Yury Ushakov, did not provide further details about the upcoming phone call.

Russian women may soon undergo a dramatic makeover if a Kremlin-friendly lawmaker has his way and pushes through a ban on a fashion item they perhaps cherish the most: high heels.

Oleg Mikheyev, a lawmaker with pro-Kremlin A Just Russia party, says vertiginous heels as well as trainers, ballet flats and men's loafers are bad for people's health and it's time to do something about it.

Russia has launched a military preparedness drill that includes moving troops in Siberia and the Urals to other locations, a military official said on Friday.

"Some motorized and air defense groups located in the Urals and Western Siberia have been put on alert and have begun multi-kilometer marches... to destination areas," said the assistant commander of Russia's central military district Yaroslav Roshchupkin, Russian agencies reported.

Ukraine's new Western-backed president on Friday released a sweeping peace plan for curbing a pro-Russian uprising in the separatist east that is threatening the ex-Soviet country's survival.

The 14-point initiative's publication followed two calls made by President Petro Poroshenko to Vladimir Putin within 72 hours in the belief that no truce could work without the support of the Russian strongman.

The number of people driven from their homes by conflict and crisis has topped 50 million for the first time since World War II, with Syria hardest hit, the U.N. refugee agency said Friday.

The UNHCR said there were 51.2 million forcibly displaced people at the end of 2013, a full six million higher than the previous year.

Russia is again building up forces on the border with Ukraine, NATO Secretary-General Anders Fogh Rasmussen said on Thursday, calling it a "very regrettable step backwards".

Rasmussen said "at least a few thousand more" Russian troops had been deployed to the border.

Russia on Thursday accused the West of attempting to torpedo Moscow's latest draft resolution on Ukraine and called on the U.N. Security Council to help alleviate the humanitarian crisis in the ex-Soviet country.

"Many Western members of the Security Council continue to look for various excuses to stall for as long as possible the work on the Russian draft which essentially opens the way for a real opportunity to launch the process of peacefully resolving the situation in Ukraine," a foreign ministry spokesman said.

Russia has arrested a 43-year-old Turkish national put on an international terrorist wanted list last year, the interior ministry said.

The unidentified man was apprehended in recent days and ordered to remain in custody by a court Tuesday, the ministry's branch in southern Volgograd region said.