Here's what you need to know about Ukraine crisis
Toward the end of the Sochi 2014 Winter Olympics, Ukraine's months-long conflict erupted into a series of violent clashes before morphing into an international crisis. Here are key events that happened in Ukraine since then.
February 22, 2014
Ukrainian President Viktor Yanukovych flees after protesters seize his Kiev office and the parliament votes to oust him. This marks the final straw after protests began in November when Yanukovych rejected an association agreement with the European Union, seeking closer ties with Moscow.
February 26, 2014
Leaders of opposition forces in Ukraine names new ministers and acting president, Oleskandr Turchynov. Just a few days following the overthrow of his ally, Yanukovych, Russian President Vladimir Putin steps up tension by ordering 150,000 troops to be ready for war near Ukraine.
February 27, 2014
Russian fighters take over Crimea—an autonomous region in Ukraine that has strong ties with Russia. Ousted president Yanukovych also takes refuge in Russia.
March 1, 2014
Moscow's parliament gives Putin the green light to invade Crimea to protect Russian interests. In response, the White House issues an official warning, criticizing Russia's violation of Ukrainian sovereignty.
March 2, 2014
Crimea mobilizes for war. NATO orders Russia to withdraw its military forces from Ukraine, hinting at further interventions to come from the international community.
March 4, 2014
U.S. Secretary of State John Kerry denounces Russia's actions and offers $1 billion in loans to Ukraine.
March 6, 2014
Crimea's pro-Russian parliament votes to join Russia and sets for a March 16 referendum. President Barack Obama orders sanctions, calling Crimea's referendum a violation of international law.
March 16, 2014
In a referendum, 95 percent of Crimea reportedly votes to separate from Ukraine and join Russia.
March 18, 2014
Going against sanctions and protests, Putin officially adds Crimea back to Russia. This happens about 60 years after then-Soviet leader Nikita Khrushchev gave Crimea to Ukraine as a gift.
March 24, 2014
Tensions deepen as G7 leaders and Obama warn Russia of further sanctions. Ukraine begins to withdraw its military forces from Crimea.
April 7, 2014
Protests ignite again. Pro-Russian forces seize a government building in eastern Ukraine and call for a referendum on seceding from Ukraine.
April 12, 2014
Ukraine says it won't be paying Russia for natural gas. Two days prior, Putin warned of disruptions in natural gas supply to Europe if Ukraine doesn't pay its bills. Ukraine owes Russia $2.2 billion.
April 15, 2014
Ukraine launches a special operation against separatists in its Russian-supporting region in the east.