Months of protests in Ukraine and deadly clashes in recent days between anti-government protesters and police culminated on Saturday with parliament voting to oust President Viktor Yanukovych.
Here are 10 things you need to know to keep up to date with the situation:
1. What are the protests about?
The protests broke out after President Yanukovych's government rejected a far-reaching accord with the European Union in November 2013 in favour of stronger ties with Russia.
Thousands of people, outraged that a long-standing aspiration for integration with Europe had been ditched overnight, poured into central Kiev for peaceful protests. They have occupied Independence Square, known as Maidan, ever since.
Several developments - including police attacks on student protesters, severe new anti-protest laws, and the abduction and beating of opposition activists - caused the demonstrations to spread and intensify.
For many, the protests were less about Europe than about getting rid of a president who they believed was clinging to power and serving the interests of his own close circle and Moscow.
2. What caused this month's deadly clashes?
The bloodshed in Kiev on Feb 20 was the worst so far. The health ministry said 77 people had been killed in 48 hours, with nearly 600 wounded.
Video showed police snipers firing live rounds at a group of protesters carrying makeshift shields.
The sudden deterioration began on Feb 18 - and took many by surprise. Both sides blamed each other, but who threw the first stone or fired the first shot is still not clear.
The government and opposition had agreed a deal - an amnesty for arrested protesters, if demonstrators vacated captured government buildings.
The opposition had also agreed - with negotiators for the president's ruling Party of the Regions - that parliament would discuss changing the constitution to reduce the president's powers. But then the speaker of parliament refused to allow that on the agenda. As news got out, angry protesters marched on parliament.
3. Who are the protesters?
The protests have been strongest in the Kiev area and western Ukraine, where there is a greater affinity with Europe to the west, rather than in the Russian-speaking east and south. But there have been protests in eastern Ukraine too.
The leaders of the three opposition parties in parliament - Vitali Klitschko of the pro-EU Udar movement; Arseniy Yatsenyuk of the main opposition Fatherland; and Oleh Tyahnybok of the far-right Svoboda - have been on the Maidan, attempting to direct the protests and trying to present a united front.
But these leaders appear not to enjoy the full trust of many protesters. The Fatherland party, in particular, is tainted by its recent years in government and seen by some as part of the political establishment.
Some radical right-wing groups, like Right Sector and Common Cause, have been at the forefront of clashes with police, though it is not clear how much support they have.
4. What is at stake?
Ukraine seems be caught in a modern "Great Game". Russia's President Vladimir Putin wants to make Russia a global economic player, rivalling China, the US and EU. To that end he is creating a customs union with other countries and sees Ukraine as a vital and natural element in that - not least because of the countries' deep cultural and historical ties.
The EU says assimilation and eventual membership could be worth billions of euros to Ukraine, modernising its economy and giving it access to the single market. It also wants to reverse what it sees as damaging infringements on democracy and human rights in Ukraine.
Many Ukrainians in the east, working in heavy industry that supplies Russian markets, are fearful of losing their jobs if Kiev throws in its lot with Brussels.
But many in the west want the prosperity and the rule of law they believe the EU would bring. They point out that while Ukraine had a bigger GDP than Poland in 1990, Poland's economy is now nearly three times larger.
5. Will Ukraine split in two?
Much has been made of the cultural-linguistic divide between Ukraine's east and west - and the way this is to some extent reflected in voting patterns.
Russian is widely spoken in parts of the east and south, and in some places, like the Crimean peninsula, is the main language. This is largely down to heavy immigration from Russia during the Soviet era.
In westernmost regions - where Poland and Austria were dominant for hundreds of years - the population speaks Ukrainian, tends to be more nationalistic and identifies with Central Europe.
6. What led to parliament voting to oust Viktor Yanukovych?
President Yanukovych signed a deal with opposition leaders after lengthy talks with the foreign ministers of three EU countries - France, Germany and Poland.
He offered early elections - to be held by December - and the formation of a new coalition government and said he was ready to reform the constitution, to return to the 2004 constitution under which parliament had more powers.
But overnight into Saturday, Feb 22, the heavily armed guard around the presidential offices slipped away and Mr Yanukovych himself was also nowhere to be seen.
It appears he had flown to Kharkiv where he gave a TV interview insisting he was still in power. But events had moved too quickly for him. His arch-rival Yulia Tymoshenko - jailed in 2011 - has been freed and has flown to Kiev, the city where President Yanukovych no longer appears to have control. Even many in his own party deserted him.
7. What is Russia's role in Ukraine?
Moscow clearly had a strong influence over Mr Yanukovych, whom it backed during the 2004 Orange Revolution when his election was ruled to have been fraudulent. To many observers, Russia has used a carrot-and-stick approach to Ukraine. It suspended its loans when the Ukrainian government resigned, and restricted trade when Ukraine looked like signing up with the EU. The EU called this "unacceptable" economic pressure.
But Russia accused the EU of trying to doing the same, using free trade with Europe as the temptation.
There are also very rich oligarchs in Ukraine, thought to have political influence behind the scenes. The richest, Rinat Akhmetov, has issued strong statements backing people's right to peaceful protest. But some oligarchs are thought to have been sidelined under Mr Yanukovych, in favour of a new group centred around his own family.
8. Who is Viktor Yanukovych?
- Born on July 9, 1950, in Yenakiyevo, Ukraine. Yanukovych is a native Russian speaker; his Ukrainian is noticeably weaker. He is married with two sons.
- Was twice convicted of violent crimes - robbery and moderate assault (1967) and assault (1970) - as a young man.
- Worked as an electrician in a bus company in the early 1970s before entering Donetsk Polytechnic Institute.
- Worked in the transportation industry in eastern Ukraine in the 1980s to 1900s, reaching senior managerial posts. He entered the Communist Party shortly after graduating from university.
- Was governor of Donetsk, an eastern, coal-producing region, from 1997-2002.
- Was Prime minister under President Leonid Kuchma from 2002-2004. At this point, Yanukovych was already being touted as a potential successor to Kuchma.
- During the Orange Revolution (Nov 2004-Jan 2005), Yanukovych defeated Viktor Yushchenko in a runoff vote that was condemned as fraudulent by the opposition. Yushchenko decisively won a court-ordered re-run of the vote.
- Was Prime minister under President Viktor Yushchenko 2006-2007. Appointed after the Orange Revolution parties failed to form a coalition.
- Elected president of Ukraine on Feb 7, 2010, defeating Yulia Tymoshenko by 3.48 percent of the vote in a runoff.
- Highlights of his tenure include the withdrawing of the hero status bestowed on wartime nationalist leader Stepan Bandera, a political balancing act between pro-Russia and pro-Western interests, and prosecutions against former opposition leaders, including Tymoshenko and Kuchma.
9. Who is Yulia Tymoshenko?
- Born in 1960 in Dnipropetrovsk, industrial city in eastern Ukraine. Trained as engineer and economist
- A slender, telegenic blonde known for wearing her long hair in an elaborately braided crown, Tymoshenko's looks belie a steely temperament that has been compared to former British prime minister Margaret Thatcher's - one of her heroines.
- Known at home as the "Iron Lady", after Thatcher, or simply by the Ukrainian word for "she" - "vona" - Tymoshenko was a leader of the 2004 Orange Revolution that forced the annulment of elections initially awarded to Yanukovych.
- But for her detractors, she is an unscrupulous political opportunist with no fixed ideas who became enormously rich in the corruption-stained 1990s and deserves what she got.
- She is loved by her supporters as an unflinching defender of Ukrainian sovereignty and its European future.
- She challenged Yanukovych in a bitterly contested 2010 presidential election, losing in a run-off and then finding herself the target of a string of criminal investigations she claimed were aimed at eliminating her from politics.
- She was first arrested in August 2011, then sentenced to seven years in October that year on charges of abusing her power in a 2009 gas deal signed with Russia during her premiership.
- Her jailing, which Tymoshenko argued was the result of a vendetta pursued by Yanukovych and his "family" of close relatives and oligarchs, prompted anger in the West and a crisis in Ukraine's relations with the European Union.
- On her release from prison in Kharkiv on Saturday, Tymoshenko announced she intended to run in the elections on May 25.
- Despite being regarded as a flawed figure, whose own political rivalries have contributed to Ukraine's problems, Tymoshenko, who enjoys cordial relations with Putin, might be viewed in Moscow as a compromise candidate able to work with the two sides, and position Ukraine between the EU and Moscow.
10. What's next?
Ukraine is far from out of the woods. Talk of secession by the Crimea and the country's east is still doing the rounds and one scenario being discussed is the annexation of Crimea by Russia. This would be a repeat performance of the occupation by Russian forces of Abkhazia in 2008 and could lead to an alarming confrontation between Moscow and whatever future government emerges in Kiev.
The sharp divide between east and west has fueled fears of a messy breakup of the country. That remains a risk, though all sides are pleading against it.
Former Prime Minister Yulia Tymoshenko is now free from 2 1/2 years in custody, and is promising to run for president. Mrs Tymoshenko is already confidently talking about joining the EU, but that prospect seems a long way off given Ukraine's corrupt economy.
While the opposition is now pushing for earlier elections than had been envisaged in the EU-brokered deal to end the violence, the May elections being asked for by some might exacerbate the crisis.
Source: BBC, CNN, The Guardian, Moscow Times, AFP