SIMFEROPOL, Ukraine — Russian armed forces seized control of Ukraine's Crimean peninsula on Saturday, as the Russian Parliament granted President Vladimir Putin broad authority to use military force in response to the political upheaval that dislodged a Kremlin ally and installed a new, staunchly pro-Western government.
Russian troops stripped of identifying insignia but using military vehicles bearing the license plates of Russia's Black Sea force swarmed the major thoroughfares of Crimea, encircled government buildings, closed the main airport and seized communication hubs. The moves solidified what began Friday as a covert effort to control the largely pro-Russian region.
In Moscow, Putin convened the upper house of Parliament to grant him authority to use military force to protect Russian citizens and soldiers in Crimea and throughout Ukraine.
President Barack Obama, who spoke to Putin on the phone, accused Russia of a "breach of international law." He condemned the country's military intervention, calling it a "clear violation" of Ukrainian sovereignty. On Friday, Obama had pointedly warned Russia to respect Ukraine's territorial integrity.
In addition to the risk of open war, it was a day of frayed nerves and set-piece political appeals that recalled ethnic conflicts of past decades in the former Soviet bloc, from the Balkans to the Caucasus.
Obama spoke with Putin for 90 minutes Saturday, according to the White House, and urged Putin to withdraw his forces back to its bases in Crimea and to stop "any interference" in other parts of Ukraine.
In a statement afterward, the White House said the United States would suspend participation in preparatory meetings for the Group of Eight economic conference to be held in Sochi, Russia, in June and warned of "greater political and economic isolation" for Russia.
The Kremlin offered its own description of the call, in which it said Putin spoke of "a real threat to the lives and health of Russian citizens" in Ukraine and warned that "in case of any further spread of violence to Eastern Ukraine and Crimea, Russia retains the right to protect its interests and the Russian-speaking population of those areas."
In Britain, Prime Minister David Cameron said that "there can be no excuse for outside military intervention" in Ukraine.
At the United Nations, the Security Council held an emergency meeting on Ukraine for the second time in two days. The U.S. ambassador, Samantha Power, called for an international observer mission, urged Russia to "stand down," and took a dig at Russian Ambassador Vitaly Churkin on the issue of state sovereignty, which the Kremlin frequently invokes in criticizing the West over its handling of Syria and other disputes.
"Russian actions in Ukraine are violating the sovereignty of Ukraine and pose a threat to peace and security," she said.
U.N. Secretary-General Ban Ki Moon also spoke with Putin on Saturday and described himself as "gravely concerned" and urged Putin to negotiate with officials in Kiev.
Former Ukrainian President Viktor Yanukovych's refusal, under Russian pressure, to sign new political and free trade agreements with the European Union last fall set off the civil unrest that last month led to the deaths of more than 80 people, and ultimately unraveled his presidency. The country's new interim government has said it will revive those accords.
Ukraine's acting president, Oleksandr Turchynov, said at a briefing in Kiev on Saturday evening that he had ordered Ukraine's armed forces "to full combat readiness." A Ukrainian military official in Crimea said soldiers had been told to "open fire" if they came under attack by Russian troops or others.
Officials in Kiev demanded that Russia pull back its forces, and confine them to the military installations in Crimea that Russia has long leased from Ukraine.
The political drama began in the morning, when the pro-Russia prime minister of Crimea, Sergei Aksyonov, declared that he had sole control over the military and the police, and appealed to Putin for Russian help in safeguarding the region. He also said a public referendum on independence would be held on March 30.
The Kremlin quickly issued a statement saying that Aksyonov's plea "would not be ignored," and within hours the upper chamber of Russia's Parliament had authorized military action.
The authorization cited Crimea, where Russia maintains important military installations, but covered the use of Russian forces in the entire "territory of Ukraine," and its time frame extended indefinitely, "until the normalization of the sociopolitical environment in the country." Parliament also asked Putin to withdraw Russia's ambassador to the United States.