The 27-year-old spent last season on loan at Southampton and his contract with Lens is set to expire next month.
“Porto and Stoke City have made enquiries,” he told France Football.
“I’m waiting to see concrete offers.
“The Portuguese club have followed me for several months now. They met my agent last winter.
“I’m not worrying about it. I’m on holiday, I’m waiting. You have to be patient. The market’s not moving much.”