The 30-year-old player, who has been capped 68 times for his country, becomes Steve Bruce's fifth signing since the transfer window opened on January 1st, after impressing greatly during a recent trial.
Earlier this week Bruce said "Over the last week he has done remarkably well. He's captain of his country, has a good pedigree and would be a good addition."
He initially joins Blues on loan until June from French First Division outfit Olympique Marseille.
Then, depending on Blues' Premiership survival and appearances, the defensive midfielder will sign a three-year deal in the summer.