Key events in Ukraine's political crisis:
Nov. 21, 2013: President Viktor Yanukovych's government announces it's abandoning an agreement to strengthen ties with the European Union and instead seeking closer cooperation with Moscow. Protesters take to the streets.
Nov. 30: Images of protesters bloodied by police truncheons spread quickly and galvanize public support for the demonstrations.
Dec. 1: A protest attracts around 300,000 people on Kiev's Independence Square, known as the Maidan, the largest since the 2004 Orange Revolution. Activists seize Kiev City Hall.
Dec. 17: Russian President Vladimir Putin announces Moscow will buy $15 billion worth of Ukrainian government bonds and cut the price Ukraine pays for Russian natural gas.
Jan. 22, 2014: Three protesters die during a confrontation between police and demonstrators manning barricades.
Jan. 28: In concessions to the opposition, the prime minister resigns and parliament repeals harsh anti-protest laws that set off the violence.
Feb. 16: Opposition activists end their occupation of Kiev City Hall in exchange for the release of all 234 jailed protesters.
Feb. 18: Protesters attack police lines and set fires outside parliament after it stalls on a constitutional reform to limit presidential powers. Riot police respond to the violence by trying to push protesters off Independence Square. At least 26 people die and hundreds are injured.
Feb. 20: Hours after a truce is announced, violence between protesters and riot police resumes. More than 80 people, mainly protesters, are killed by gunshots.
Feb. 21: Under a European-mediated plan, protest leaders and Yanukovych agree to form a new government and hold an early election. Parliament slashes his powers and votes to free his rival, Yulia Tymoshenko, from prison. Yanukovych flees Kiev after protesters take control.
Feb. 22: Parliament votes to remove Yanukovych and hold new elections. Tymoshenko is freed and addresses tens of thousands on the Maidan.
Feb. 23: Ukraine's parliament assigns presidential powers to its new speaker, Oleksandr Turchynov, a Tymoshenko ally. The new authorities ask the West for loans to avoid an imminent default. Pro-Russia protesters start rallying against the new authorities in Crimea, where Russia has a major naval base.
Feb. 24: Ukraine's interim government draws up a warrant for Yanukovych's arrest. Russian Prime Minister Dmitry Medvedev derides the new leaders in Kiev as "Kalashnikov-toting people in black masks."
Feb. 26: Leaders of Ukraine's protest movement propose legislator Arseniy Yatsenyuk as prime minister. In Moscow, Putin orders major military exercises just across the border.
Feb. 27: Masked gunmen seize regional parliament and government buildings in Crimea. Ukraine's government pledges to prevent a national breakup with strong backing from the West. Yanukovych is granted refuge in Russia.
Feb. 28: Ukraine says Russian troops have taken up positions around strategic locations on the Crimean Peninsula. Ukraine's parliament adopts a resolution demanding that Russia halt steps it says are aimed against Ukraine's sovereignty and territorial integrity. Turchynov says he has put armed forces on full readiness because of the threat of "potential aggression."
March 1: Troops under apparent Russian command take over Crimea without firing a shot. The Kiev government and its Western supporters are powerless to react. President Barack Obama calls Putin to demand the troops' withdrawal.
March 2: Ukraine appeals for international help, fearing a wider Russian invasion. Supporters on both sides take to the streets of Ukrainian cities and of Moscow. The Group of Seven suspends preparations for June's Group of Eight summit in Russia.
March 3: Ukraine says there are up to 16,000 Russian troops in Crimea. Russia says it has approved troop deployment at the request of Yanukovych. The main Russian stock index falls 12 percent; Russia's central bank raises its main interest rate 1.5 percentage points.
March 6: Crimea's parliament declares the region wants to join Russia and will let voters decide in a March 16 referendum.
March 11: The EU proposes a package of trade liberalization measures to support Ukraine's economy, abolishing most import tariffs on the country's products — a step expected to save the country's exporters 500 million euros ($695 million) annually.
March 12: Obama meets with Yatsenyuk in Washington in a show of support for the new Ukrainian government and declares the U.S. would "completely reject" the Crimea referendum.
March 14: A last-ditch diplomatic effort before the referendum fails in London, where Russian Foreign Minister Sergey Lavrov met with U.S. counterpart John Kerry amid threats of sanctions against Russia if it annexes Crimea.
March 16: Crimea votes in the referendum about whether to become independent and seek to become part of Russia.
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