Ukraine leader urges Putin to pull back military
Troops with no insignia on their uniforms have already seized Crimea, an isolated peninsula on the Black Sea where Russia has a large military presence.
In the coastal town of Balaklava, Russian-speaking troops in vehicles with black Russian number plates had encircled a small garrison of Ukrainian border guards.
Russian troops have also taken weapons from a radar base and a naval training facility, according to reports from the Interfax news agency.
On Saturday, Russian President Vladimir Putin demanded and won parliament's approval to invade Ukraine.
Kiev responded by putting its troops on high alert and appealed to NATO for help.
Ukraine's new prime minister is urging Putin to pull back his troops, saying "we are on the brink of disaster."
Arseniy Yatsenyuk spoke after a closed session of his new parliament in Kiev, calling on Putin to "pull back his military."
Pope Francis is urging world leaders to promote dialogue as a way of resolving the crisis in Ukraine.
Speaking to thousands of people in St. Peter's Square during his traditional Sunday midday appearance, he said: "I am making a heartfelt appeal to the international community: support every initiative for dialogue and harmony."
Francis urged all segments of Ukrainian society to work together to overcome their misunderstandings and build a future together.