Slimani enjoyed an outsanding season last year, scoring 27 goals in 33 games in Portugal's top flight.
The Algerian has also played 43 times for his country and has scored 23 international goals.
The 'Guardian' is also reporting that West Brom have had a bid rejected for the striker in the past week.
Leicester have scored just three goals in the Premier League this season and Claudio Ranieri is clearly looking to add firepower to his front line.