"We are committed to Ukraine's sovereignty and territorial integrity and will continue to provide Ukraine the support it needs," a senior State Department official said.

Poroshenko was greeted by several thousand cheering supporters. Some carried banners reading "We need democracy," and "Stop repressions."

A message posted by hackers in Ukrainian, Russian and Polish warns Ukrainians that their personal data has been breached and to "be afraid and expect the worst."

Russia forced the West into a flurry of diplomacy this week with its massive troop buildup on its border with Ukraine. Here's a short guide to what the Kremlin wants.

In nearly eight hours of talks with U.S. officials, Russia says it's not planning to attack Ukraine, despite have an estimated 100,000 troops near the border. More talks are expected.

Russia's Interfax news, citing the military, reports that 10,000 troops are returning to their "permanent deployment points" from the border region.

Russia forcibly annexed Crimea from Ukraine in 2014. The international community does not recognize Russian sovereignty over the peninsula.