The United States says Russia is moving troops into Ukraine's Crimea Peninsula by ferry, after Russian soldiers on Monday seized a border post on the Ukrainian side of a waterway separating the two countries.
Washington's United Nations Ambassador Samantha Power confirmed the troop movement Monday at an emergency meeting of the U.N. Security Council in New York. Earlier Monday, Reuters news agency quoted Ukraine border guards as saying they had seen Russia assembling an armored column on its side of the Kerch Strait.
Russian Ambassador Vitaly Churkin used the Council session to read a statement from Ukraine's ousted pro-Russian president Viktor Yanukovych, who fled Kyiv for Russia last week after weeks of anti-government protests.
Churkin said Yanukovych has asked Russian President Vladimir Putin to intervene militarily in Ukraine to establish "peace" and "stability" in his homeland. For his part, Mr. Putin insists Moscow has the right to intervene in Ukraine to protect Russian citizens.
Earlier Monday, the U.S. State Department said Washington is preparing to impose sanctions on Moscow. Spokeswoman Jen Psaki did not elaborate.
European Union Council President Herman Van Rompuy said EU leaders will hold an extraordinary meeting on the Ukraine crisis Thursday in Brussels.
U.S. Vice President Joe Biden spoke Monday by telephone with Russian Prime Minister Dmitry Medvedev. The White House said Biden urged Russia to withdraw its forces from Ukraine, support the immediate deployment of international monitors and begin a "meaningful political dialogue" with the Ukrainian government.
Russian media quoted Mr. Medvedev's press secretary as saying that the call was initiated by the United States and the Russian prime minister stressed the need to "protect Ukrainian citizens, including in Crimea, as well as citizens of the Russian Federation located on the territory of Ukraine."
Russian Foreign Minister Sergei Lavrov said Monday that the use of Russian troops in Crimea is necessary "until the normalization of the political situation" on the peninsula. He spoke at the opening of the U.N. Human Rights Council session in Geneva and said his country's troops are protecting Russian nationals.
Lavrov met Monday with U.N. Secretary-General Ban Ki-moon, who is hoping to prevent a further escalation in the region.
Russia's foreign ministry on Monday strongly criticized the Group of Eight major industrialized nations for suspending preparations for the G8 summit schedule to take place in the Russian city of Sochi in June over the events in Ukraine. The ministry said in a statement the move damages not only the G8 countries, but "the whole international community."
In a separate statement Monday, Russia's foreign ministry criticized what it called "unacceptable threats" made by U.S. Secretary of State John Kerry, who on Sunday called Russia's dispatch of troops to Crimea "a brazen act of aggression, in violation of international law."
British Foreign Secretary William Hague is in Ukraine to meet with leaders, and on Monday visited Kyiv's Independence Square. He said in a BBC radio interview that Russian forces have taken "operational control of the Crimea" and that they must return to their bases there.
Kerry is due to travel Tuesday to Ukraine.
Crimea is a Black Sea peninsula placed under Ukrainian control in 1954 by then-Soviet leader Nikita Khrushchev. It remained part of Ukraine when the Soviet Union collapsed in 1991. Crimea has a tiny border with Russia on its far eastern point. The Crimean port of Sevastapol is home to Russia's Black Sea fleet. 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.