TIMELINE

Key events in Ukraine’s political crisis:

Nov. 21, 2013: President Viktor Yanukovych's government announces it is abandoning an agreement to strengthen ties with the European Union, instead seeking closer cooperation with Moscow. Protesters take to the streets.

Dec. 1: A protest attracts about 300,000 people on Kiev's Independence Square, known as the Maidan. 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 Ukrainians pay for Russian natural gas.

Jan. 28, 2014: In concessions to the opposition, the Ukrainian 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. At least 26 people die and hundreds are injured.

Feb. 20: Hours after a truce is announced, violence resumes, with government snipers shooting protesters from the roofs. Most of the 82 deaths occur on this day.

Feb. 21: 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.

Feb. 23: Ukraine's parliament assigns presidential powers to its new speaker, Oleksandr Turchinov. 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.

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 on the Crimean peninsula.

March 1: Russian troops take over Crimea. The Kiev government and its Western supporters are powerless to react. U.S. President Barack Obama calls Putin to demand the troops' withdrawal.

March 2: Ukraine appeals for international help, fearing a wider Russian invasion.

March 3: Pro-Russian troops control a ferry terminal on the easternmost tip of Crimea, adding to fears that Moscow is planning to bring in even more troops.

— Associated Press

DEVELOPMENTS

— Ukraine’s mission to the United Nations claimed Monday that 16,000 Russian troops have been deployed in the Crimea region, while Russia’s U.N. ambassador told an emergency Security Council meeting that Ukraine’s fugitive president requested them.

— President Barack Obama is considering economic and diplomatic options to isolate Russia. He called on Congress to work on an aid package for Ukraine.

— European Union leaders called a special summit for Thursday, where they are expected to freeze visa liberalization and economic cooperation talks with Russia if Moscow hasn’t taken steps to calm the crisis in Ukraine’s Crimean peninsula.

— The United States will not send a presidential delegation to the Paralympic Games in Sochi, Russia. White House spokeswoman Caitlin Hayden says Obama still supports the U.S. athletes participating and wishes them success.

Russia called for a national unity deal in Ukraine even as it tightened its stranglehold over Crimea, a bold combination of diplomacy and escalating military pressure. The U.S. and European Union floundered for solutions — while global markets panicked over the prospect of violent upheaval in the heart of Europe.

Fears grew in the Ukrainian capital and beyond that the Kremlin might carry out more land grabs in pro-Russian eastern Ukraine, adding urgency to Western efforts to defuse the crisis. U.S. Secretary of State John Kerry was heading to Kiev in an expression of support for Ukraine’s sovereignty, and the EU threatened a raft of punitive measures as it called an emergency summit on Ukraine for Thursday.

But it was Russia that appeared to be driving the agenda.

Foreign Minister Sergey Lavrov said at a U.N. Human Rights Council session in Geneva that Ukraine should return to an agreement signed last month by pro-Russian President Viktor Yanukovych — but not Moscow — to hold early elections and surrender some powers. Yanukovych fled the country after sealing the pact with the opposition and foreign ministers of France, Germany and Poland.

“Instead of a promised national unity government,” Lavrov said, “a government of the victors has been created.”

Meanwhile, Ukrainian authorities said that Russian troops had issued an ultimatum for two Ukrainian warships to surrender or be seized — prompting the country’s acting president to accuse Russia of “piracy.”

Ukraine’s corvette Ternopil and the command ship Slavutych were being blocked by four Russian navy ships in Sevastopol’s harbor, a Ukrainian military spokesman said. Acting president Oleksandr Turchynov said commanders and crew were “ready to defend their ships. … They are defending Ukraine.”

Vladimir Anikin, a Russian defense ministry spokesman, dismissed the report of a Russian ultimatum as nonsense, but refused to elaborate.

Warning of a “dangerous escalation,” the Obama administration said Washington would hold Moscow directly accountable for any threat to Ukraine’s navy.

Russia is “on the wrong side of history” in Ukraine, President Barack Obama said, adding that continued military action would be “a costly proposition for Russia.” Speaking to reporters in the Oval Office, Obama said the U.S. was considering economic and diplomatic options that will isolate Russia, and called on Congress to work on an aid package for Ukraine.

Still, it was not clear what the West could do to make Russia back down. The clearest weapon at the disposal of the EU and U.S. appeared to be economic sanctions that would freeze Russian assets and pull the plug on multibillion-dollar deals with the country. Late Monday, the EU threatened to freeze visa liberalization and economic cooperation talks and boycott the G8 summit in Russia if Moscow does not back down.

By Monday, it was clear that Russia had complete operational control of Crimea.

Russian soldiers controlled all Crimean border posts, as well as all military facilities. Troops also controlled a ferry terminal in the Crimean city of Kerch, just 12 miles across the water from Russia, intensifying fears that Moscow would send more troops via that route.

Border guard spokesman Sergei Astakhov said the Russians were demanding that Ukrainian soldiers and guards transfer their allegiance to Crimea’s new pro-Russian local government.

He said four Russian military ships, 13 helicopters and eight transport planes had arrived in Crimea in violation of agreements that permit Russia to keep its Black Sea fleet at the naval base in Sevastopol but limits the deployment of additional forces at the base.

Ukraine’s prime minister admitted his country had “no military options on the table” to reverse Russia’s military moves into Crimea.

Already the economic fallout for Russia was being felt: the main RTS index was down 12 percent, at 1,115, and the dollar spiked to an all-time high of 37 rubles. Russia’s central bank hiked its main interest rate 1.5 percentage points Monday to 7 percent, trying to stem financial outflows. But the economic consequences were also acute for Western Europe: The EU relies heavily on Russian natural gas flowing through a network of Ukrainian and other pipelines.

Market reaction to the Russian seizure was furious Monday. On Wall Street, both the Dow Jones industrial average and the Nasdaq composite closed sharply down, while oil prices rose on fears that Russia, a major oil exporter, might face sanctions. In European trading, gold rose while the euro and stock markets fell.