With Russian President Vladimir Putin asking for parliamentary approval for a troop deployment in Ukraine and pro-Russian forces tightening their grip on Crimea, the turmoil in Ukraine is turning into a full-blown international crisis.
The BBC's reporters on the ground cover the latest developments.
Ukraine's Acting President Oleksander Turchinov has called an emergency meeting of his security chiefs, report correspondents
The tension in Crimea is increasingly militarised
Christian Fraser watched a Russian navy vessel at Balaklava on Friday
The crisis is turning into a fast-moving game of geopolitical chess
The mood in Kiev is very against any Russian intervention, say correspondents
On Friday, ousted President Viktor Yanukovych asked for Russian help - but not invasion
It is unclear what Russia's response will mean in practice
President Putin makes his move
The question everyone is asking
The autonomous province of Crimea is home to 2.3 milion people, and no small number of military bases
Amid claim and counter-claim, it increasingly appears as though Russia might be preparing to move
The Russian parliament is calling for boots on the ground to protect its Black Sea fleet
Despite the calm on the streets of Crimea, military tension is rising sharply
The backlash is building
Anti-government protesters are taking to the streets across eastern and southern Ukraine, correspondents report
The new government's problems are not limited to Crimea
The BBC's Daniel Sandford says "what appear to be Russian troops" are standing guard at local government offices in Simferopol
Security seems to be the watchword across the country now
Correcting a previous tweet saying there were none there, Daniel Sandford reports there are armed men at Crimea's Krym TV station
Pro-Russian demonstrators make their point outside the police headquarters in Crimea's capital
Most of Crimea's population are ethnic Russian
Things appear to be less tense on the ground today, despite increased diplomatic pressure internationally
The armed men guarding buildings in Crimea are equipped with military hardware
None of the armed men controlling key institutions have left their posts since they first moved in
President Putin offers a hint of what his next move might be
Sergiy Aksyonov: "I call on the president of the Russian Federation, Vladimir Putin, to provide assistance in securing peace"
Crimea was part of Russia until the 1950s, and still has very close ties with the country
"Temporary" was not defined
Crimea's newly installed leader tightens his grip on the province
Christian Fraser reports on the start of the process in which armed men took over most of Crimea's key institutions
Opponents of the new government in Kiev often say the opposition are fascists. They are not wrong about all of them. Go to BBC Newsnight on YouTube for the full report.
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