The crisis in Ukraine is now focused on the majority Russian region of Crimea. Two airports have been occupied by armed men, who the Ukrainian authorities say are linked to the Russian military.
BBC reporters at the scene have been providing regular updates.
In the long-awaited news conference, Viktor Yanukovych insists he remains Ukraine's legitimate leader
Far-right Russian politician Vladimir Zhirinovsky is not known for quiet diplomacy
Ukrainian, not Russian, flags hang behind the seat Viktor Yanukovych will sit in, in this photo by Yuri Maloveryan (@MaloverjanBBC)
All eyes are now on Viktor Yanukovych's news conference
Security is tight, as crowds of journalists arrive for Viktor Yanukovych's press conference - and are thoroughly searched on their way in, reports the BBC's Yuri Maloveryan
Balaklava is an important port in Crimea, hence the interest in what the Russian navy might be doing there
Troops are on the move in Crimea, reports the BBC's Daniel Sandford
As the Russia's Back Sea fleet is based in Crimea it is not unusual to see naval ships there, but the movements of some ships has drawn speculation there might be more to it
Russia's lease on the Sevastopol base lasts until 2042 - a source of controversy among more nationalist, anti-Russian Ukrainians, say correspondents
At 07:00 Daniel Sandford tweeted this picture of men in unmarked uniforms at Simferopol airport
In mid-morning Ukraine time, Christian Fraser sent this report from the barriers blocking access to Sevastopol's military airport
The armed men at Simferopol airport would not identify themselves as Russian or Ukrainian
Amid claims and counter claims, this is the question on everyone's lips
Despite reported Russian military insignia on the uniforms of the armed men at Sevastopol's military airport, the local Black Sea fleet denies involvement
Also by late morning (Ukraine time), it was not only the airports being occupied, according to Russian and Ukrainian media
Correspondents say Crimea is a centre of pro-Russian sentiment. The majority of its 2.3 million inhabitants identify themselves as ethnic Russians and speak Russian as a first language
Crimea was until 1954 part of Russia, and there are some who would like it back
This short video gives a a quick history of Crimea
Crimea has a special resonance for poetry fans. "The Charge of the Light Brigade" by Alfred Lord Tennyson, is a classic about a particularly bloody part of the Battle of Balaklava during the Crimean War
The airport occupations follow a similar action against the autonomous region's parliament on Wednesday, which Mark Lowen witnessed
On Wednesday, Daniel Sandford reported on ''massive military exercises with tanks and fighter jets'' by Russia, near Ukraine's border
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