This paper deals with the design of closed loop strategies for a class of two players zero-sum linear quadratic differential games, where each player does not know exactly the state equation and model it through a system subject to norm-bounded uncertainties. The finite horizon and the infinite horizon problems are both solved: it turns out that the optimal strategies, guaranteeing to each player a given level of performance, require, to be evaluated, the solution of two scaled differential (algebraic in the infinite horizon case) Riccati equations. A numerical example illustrates an application of the proposed technique.