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.
In an address to parliament, Prime Minister Arseniy Yatsenyuk warned that "we are on the brink of disaster." He spoke as Russian troops bolstered their presence on Ukraine's Crimean peninsula, and Western governments issued repeated condemnations of the Russian deployments.
With Russian forces surrounding Ukrainian airports and military bases, Germany said Russian President Vladimir Putin has agreed with Chancellor Angela Merkel to set up a fact-finding mission on Ukraine.
A German government spokesman did not provide details. But he said the mission and an accompanying "contact group" aimed at generating Ukrainian-Russian dialogue could be led by the Organization for Security and Cooperation in Europe -- the continent's largest conflict management and crisis prevention group.
Earlier Sunday, Russian news agencies said President Vladimir Putin told U.S. President Barack Obama late Saturday that Moscow reserves the right to protect ethnic Russians in Crimea and eastern Ukraine.
In Kyiv, 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, Russia's Interfax news agency quoted Crimean parliament speaker Volodymyr Konstanynov as saying parliament will decide Monday on the date of a Crimean referendum that will give voters a choice between independence from Ukraine, continued autonomy within Ukraine or annexation by Russia. The vote was originally set for May 25, but the report said it could be moved up to March 30.
In Washington, President Obama spoke with British Prime Minister David Cameron, German Chancellor Angela Merkel, and Polish President Bronislaw Komorowski in a separate phone calls. The leaders expressed ``grave concern'' over Russia's intrusion into Ukraine.
U.S. Secretary of State John Kerry blasted the Russian deployments, calling them "an incredible act of aggression." He warned of potential economic sanctions against Moscow for military actions he likened to "19th century" behavior on a "completely trumped-up pretext." Officials in Washington say Kerry will travel to Ukraine on Tuesday to meet with its new leaders and lawmakers, and to restate U.S. economic and diplomatic support for Ukraine.
Also Sunday, dozens of protesters gathered outside the Russian Embassy in Washington D.C. to demand Russians leave Ukraine alone.
Ukraine's top security official, Andriy Paruby, says military reservists are 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, the Secretary-General has asked his deputy Jan Eliasson to travel to Ukraine immediately to ascertain the situation on the ground.
Ukrainian Ambassador Yuriy Sergeyev said 15,000 Russian troops are already in Crimea. His Russian counterpart, 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 Tatars 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.