Is Vladimir Putin preparing to invade Ukraine?

As Russian soldiers continue to amass near the Ukrainian border shots are already being fired and there are fears that President Putin is planning an invasion, says Luke Harding

Ukrainian soldiers are digging themselves into trenches along their country's border with Russia as tensions mount and fears of an invasion ordered by Moscow continue to grow.

The Guardian's senior foreign correspondent Luke Harding tells Michael Safi that the conditions on the ground would be familiar to soldiers more than a century ago in the first world war: mud, corrugated metal sheeting and barbed wire. But in the skies above, high-tech drones whiz around surveying the landscape and threatening those below.