During a phone conversation Sunday with German Chancellor Angela Merkel, Putin "directed her attention to the unrelenting threat of violence from ultranationalist forces (in Ukraine) that endangered the life and legal interests of Russian citizens," according to a Kremlin statement.
The statement also said "the measures taken by Russia are fully adequate with regard to the current extraordinary situation."
Ukraine's new government came to power last week following months of pro-democracy protests against a pro-Russian president, Viktor Yanukovych, and his decision to turn Ukraine toward Russia instead of the EU. Yanukovych fled to Russia after more than 80 people were killed in the protests. He insists he's still president.
Ukraine's acting president, Oleksandr Turchynov, put Ukraine's armed forces on alert, calling up reserves for training and stepping up security at nuclear power plants, airports and other strategic locations. However, no overt military actions by Ukraine were seen.
Turchynov also moved to consolidate the new government's authority in eastern Ukraine, appointing 18 new regional governors and enlisting the support of the wealthy businessmen known as oligarchs. The new appointees included two oligarchs in the eastern cities of Dneprotrovsk and Donetsk, as big business and the new Ukrainian government united against Russia.
Ukraine's richest man, Rinat Akhmetov, urged business, ordinary people and the government to join together, saying Sunday that the use of force and "illegal action from outside" were "impermissible."
"I call upon all my fellow citizens to unity for the sake of a whole and undivided Ukraine ... Our strength is in the solidarity of business, government and society," said Akhmetov, whose SCM Group has 300,000 employees and interests in steel, coal and mining.
Faced with the threat from Russia, "the national elite has consolidated around the new government," political analyst Vadim Karasyov of the Institute for Global Strategies told The Associated Press. "The biggest businessmen and oligarchs have agreed to head key regions. This is a very good sign for the new government."