The Czech international has struggled to cement his place in the Lyon side after the development of French youngsters Ben Arfa and Benzema as well as the ever present Fred.
The former Liverpool and Villa man was expected to make a move back to the Premier League sooner rather than later after he was strongly linked with Harry Redknapp's Portsmouth.
He has joined Pompey as cover for Kanu and Utaka who are at the African Cup of Nations and he is expected to be put straight into the deep end as he will probably make his debut against Man United in midweek.