President Vladimir Putin signed a decree on Monday recognizing Crimea as a sovereign state after the Ukrainian region's pro-Russian leaders declared it independent and applied to join Russia following a controversial referendum on Sunday.
The decree posted on the Kremlin's website appeared to be a first step toward integrating Crimea into the Russian Federation.
The decree, which took effect immediately, says Moscow's recognition of Crimea as an independent state is based on "the will of the people of Crimea."
Crimea's leaders declared a 97-percent result in favor of seceding from Ukraine in a vote condemned as illegal by Kyiv and the West. The Crimean parliament formally proposed that Russia "admit the Republic of Crimea as a new subject with the status of a republic."
Putin will address the issue at a special joint session of the Russian parliament on Tuesday.
◆ U.S. Imposes Sanctions
Hours earlier, President Barack Obama imposed sanctions on key individuals Washington deems responsible for the Crimea referendum which has been widely viewed as having been orchestrated from Moscow.
Speaking at the White House, Obama announced that he ordered sanctions against 11 Russian and Ukrainian officials, including two top advisers to Russia's President Vladimir Putin, in addition to ousted Ukrainian President Viktor Yanukovych. All will be subject to asset freezes.
In an executive order issued earlier, Obama said that the policies and actions of the Russian Federation have been found to "undermine democratic processes and institutions in Ukraine; threaten its peace, security, stability, sovereignty, and territorial integrity; and contribute to the misappropriation of its assets, and thereby constitute an unusual and extraordinary threat to the national security and foreign policy of the United States."
He said Washington stands ready to impose further sanctions if necessary, if Russia chooses to escalate the situation.
Obama also pledged "unwavering" U.S. support for Ukraine, following Crimea's moves toward joining the Russian Federation.
Obama said Vice President Joe Biden leaves for Europe later Monday to discuss the situation with NATO allies. The president himself is slated to to go Europe next week.
The speaker of Russia's upper house of parliament, Valentina Matviyenko, herself a target of the U.S.-imposed sanctions, has denounced them as "political blackmail."
◆ U.S. Sanctions Against Putin Not Ruled Out
The Obama administration does not rule out any Russian officials as possible future targets for U.S. sanctions over the Ukraine crisis, a White House spokesman said on Monday when asked whether Russian President Vladimir Putin could later be subject to punitive measures.
"The authority exists to apply sanctions to a variety of individuals and entities," White House press secretary Jay Carney told reporters. "We're not going to rule out individuals or rule out actions."
Putin himself was not named among the group of 11 Russian and Ukrainian officials against whom U.S. sanctions were imposed.
◆ EU Measures
Separately, European Union foreign ministers have agreed to impose sanctions, including travel bans and asset freezes, on 21 officals from Russia and Ukraine.
After a meeting lasting around three hours, the EU's 28 foreign ministers quickly reached agreement on the list of those to be sanctioned for their part in Russia's seizure of Crimea and Sunday's referendum to secede from Ukraine and join Russia.
In a related move, the EU has begun discussing the need to reduce its reliance on Russian energy, British Foreign Secretary William Hague said on Monday.
"We have started today discussing the longer term, the need to reduce European dependence on Russian energy over many years to come," Hague said on Sky News after a meeting of European Union foreign ministers in Brussels.
Hague also said more names could be added to the sanctions list of 21 Russians and Ukrainians imposed by the EU. He said the scope of future sanctions would depend on how Russia reacted to Crimea's application to join Russia following Sunday's referendum.
In addition to responses from the U.S. and the EU, NATO released a statement Monday calling the Crimea referendum "illegal and illegitimate." It said the vote violates the Ukrainian constitution and international law, and added that the circumstances under which the referendum was held were "deeply flawed and therefore unacceptable."
◆ Kyiv Reacts
In Kyiv, Ukraine's interim Prime Minister Arseniy Yatsenyuk -- speaking at an emergency cabinet meeting -- called the Moscow-backed Crimea vote "a circus spectacle" directed at gunpoint by Russia.
Ukraine's parliament endorsed on Monday a plan to mobilize 40,000 reservists to counter Russia's "blatant aggression" in Crimea. Some 20,000 of the country's national guard troops have also been mobilized.
Also on Monday, Ukraine recalled its ambassador to Russia for consultations.
"In connection with the situation in Crimea and the necessity of discussing some of its international aspects, the Ukrainian side is recalling its ambassador to the Russian Federation...," the Foreign Ministry in Kyiv said.
◆ Ukraine, EU to Sign Pact
Ukraine will sign an agreement on closer political cooperation with the European Union on Friday, leaving the signing of a more far-reaching trade accord for later, the EU said on Monday.
EU foreign ministers said in a statement after meeting in Brussels that they looked forward to the signing of the political provisions of the so-called association agreement that Ukraine had negotiated with the 28-nation EU, on March 21.
The agreement is expected to be signed on the sidelines of an EU summit being held in Brussels that day.
Now ousted Ukrainian president Viktor Yanukovych turned his back on signing the association agreement in favour of closer ties with Moscow last November, prompting months of street protests that eventually led to his fleeing the country.
◆ Russia Rejects UN Report
Russia rejected as biased on Monday an assessment by a United Nations official who questioned accusations that Ukraine's Russian-speaking population faced systematic human rights abuses.
The Russian Foreign Ministry statement criticized UN Assistant Secretary General for Human Rights Ivan Simonovic who said last week there had been violations against ethnic Russians in Ukraine but said there was no evidence they were "widespread or systematic."
"The biased, prejudiced and unobjective assessment of Simonovic on the human rights situation in the country calls forth surprise and confusion," said the ministry in a statement.
Russia has effectively seized control of Ukraine's broadly Russian-speaking Crimea region. There are also large Russian-speaking populations in the east of the country.
The statement also criticized Simonovic for a statement of concern over the state of human rights for ethnic Tatars in Crimea.
Russia has been justifying its incursion into Crimea as necessary to protect the rights of ethnic Russians living on the peninsula.
◆ Reactions in Ukraine's Capital
Thousands of Ukrainians gathered in central Kyiv Sunday to voice opposition to the referendum and what the perceive as Moscow's moves to divide the Ukraine.
But the mood was somber as many Ukrainians feel helpless against Russia's might and military superiority, many fearing a further escalation of tensions.
Irina, a restaurant manager who only gave her first name, said Crimea's fate likely was already decided in Moscow.
She said none of this was right. This could have been done in a nice way, in an honest way, she said. This could have been done in a constitutionally correct way. And it seems to me, she said, everyone would have agreed to that.
Moscow claims it is protecting ethnic Russians from persecution by Ukrainian "extremists" who it says illegitimately came to power after months of anti-government protests.
Another Kyiv resident, Ira, who also only gave her first name, said she had nothing against Russians.
She said she loves and respects the Russian people as much as Ukrainians, but not their government. She expressed hope that everything ends well, everyone becomes united, and that Crimea remains with Ukraine.