Military action
Russian forces have invaded Ukraine, with missile strikes and explosions reported near major cities and on its military infrastructure.
The Ukrainian military says it has killed about 50 Russian "occupiers" and shot down at least six Russian aircraft, although this has not been independently verified.
On its side, Russia claims it has met little resistance and claims that Ukrainian armed forces are fleeing en masse, abandoning their weapons and positions.
BBC
Civilian impact
Emergency sirens have been sounding in Kyiv since the first explosions in the early hours. Huge traffic jams have built up as residents try to flee the city after Ukraine closed its airspace to civilian flights.
Elsewhere, residents are seeking shelter in stations - and queues have formed for buses, cashpoints and petrol.
Several European countries bordering Ukraine, including Poland, Slovakia and Hungary, say they are preparing for an influx of refugees.