The invention relates to a method for producing an antimicrobial fabric or yarn, said method comprising the steps of immersing a fabric or yarn in an aqueous solution of a metal salt while simultaneously subjecting said solution to ultrasonic radiation; and removing the fabric or yarn from said solution and subsequently converting the metal salt in situ in the fabric or yarn into metal oxide nanoparticles, preferably via chemical and heat treatment. Fabrics and yarns obtained or obtainable by such method are also provided. In a further aspect the invention provides an apparatus for performing such method.