Keira Knightley felt ''powerless'' when she visited South Sudan.

The 29-year-old actress recently visited the war-torn country in North Eastern Africa with Oxfam and couldn't believe the devastation and fear she witnessed firsthand.

She said: ''I try to keep abreast of current affairs and what's going on around the world, and you think you get used to images of conflict and poverty.

''But standing in the middle of a refugee camp, with thousands of people crushed into an area you could walk around in 20 minutes, where there's raw sewage everywhere and where the latrines have collapsed because the rainy season has hit, it really makes you go, 'F**k, this is horrendous'. The fear in the air is palpable, but you feel powerless.''

Keira's visit has shocked her so much that she is determined to help the relief effort in any way she can.

She explained to Stylist magazine: ''It made me realise how fortunate I am to live where I do and to have had the life that I've had, but also that, emotionally, we are essentially all the same ... Being in this terrible situation yet still making the best of what you've got takes incredible strength.''