Ukraine's interim government ordered a full military mobilization Sunday, in an effort to counter what its new prime minister says is a Russian act of war.
Prime Minister Arseniy Yatsenyuk, in an address to parliament, warned lawmakers "we are on the brink of disaster." He spoke as Russian troops continued to take up positions on Ukraine's Crimean peninsula, and Western governments issued repeated condemnations of the Russian deployments.
NATO convened an emergency session Sunday to discuss the crisis, which Secretary-General Anders Fogh Rasmussen said is threatening peace and stability across Europe. He urged Moscow to "de-escalate" the tension in the region.
The White House said President Barack Obama was to discuss the crisis Sunday with Western allies. Russian news agencies said Russian President Vladimir Putin told Mr. Obama late Saturday that Moscow reserved the right to protect ethnic Russians in Crimea and eastern Ukraine.
In Kyiv, meanwhile, prosecutors have opened a treason case against the newly-appointed head of Ukraine's Black Sea fleet, after he renounced his post and swore allegiance to pro-Russian leaders in Crimea. Authorities said Admiral Denis Berezovsky, appointed Saturday, offered no resistance later in the day when his headquarters in Sevastopol were surrounded by Russian troops.
Elsewhere Sunday, U.S. Secretary of State John Kerry blasted the Russian deployments, calling them "an incredible act of aggression." Speaking in Washington, he warned of potential economic sanctions against Moscow for military action he likened to "19th century" behavior on a "completely trumped-up pretext." He also told CBS television that Moscow still has "a right set of choices" that can be made to defuse the crisis.
Ukraine's top security official, Andriy Paruby, says military reservists were mobilized to "ensure the security and territorial integrity of Ukraine." But many Western analysts are questioning the effectiveness of the call up, saying Ukraine's limited military capabilities are no match for Russian military might.
At the United Nations, Ukrainian Ambassador Yuriy Sergeyev said 15,000 Russian troops are already in Crimea under the pretense of protecting Russian citizens.
Russian Ambassador Vitaly Churkin blamed the West for ratcheting up tensions in Ukraine and backing protests that ousted President Viktor Yanukovych last month.
Crimea is a Black Sea peninsula placed under Ukrainian control in 1954 by then-Soviet leader Nikita Khrushchev. It became part of Ukraine when the Soviet Union collapsed in 1991. Crimea has a tiny border with Russia on its far eastern point. Most of the people living in Crimea are ethnic Russians, but the region also is home to ethnic Muslim Tartars who generally show disdain for Russia.
Ukraine's troubles began in November when President Yanukovych backed out of a trade deal with the European Union in favor of closer ties and economic aid from Russia. The move triggered weeks of pro-Western demonstrations in Kyiv and elsewhere in Ukraine, and forced the pro-Russian Yanukovych to flee the capital in late February.