Try spraying some lock oil into the locks then gently try to turn them with the key. Dont force it, take your time and just wiggle the key back and forth. It may need a second dose of oil
If you cant get lock oil use a good penetrating oil such as PlusGas.
Avoid WD40, I find that stuff just washes off the good oil and leaves a sticky residue after a short time.
horst
June 2011