Ukraine crisis: Will war return?

Pro-Russian rebels control broad swathes of eastern Ukraine. A fragile ceasefire with government forces could end at any time and return the region to deadly conflict.

Ukraine's Western allies accuse Russia of sending in troops and armour to help the rebels - an allegation repeatedly denied by the government in Moscow.

Some 4,000 people have already lost their lives in a crisis that few saw coming.

BBC News looks at the background to the crisis - in 60 seconds.

Video produced by Michael Hirst.