1998 Toyota Corolla Flashing Seat Belt Lights

Hi, since last month the seat belt lights in my car have started flashing, and the light does not go off even after fastening the seat belt(s) properly. This started happening all of a sudden, and now the lights don't go off.
What could be the problem? And, what's the best fix for it? Is this a small electrical probem, or a safety concern?
Thank you for your expert advice.
Regards,
Sam