Manchester City have booked their place in the fourth round of the Carling Cup with a 2-0 win at home to holders Birmingham City.

Owen Hargreaves, making his debut after an injury-ravaged three years, fired City into the lead at 17 minutes when he struck the ball into the top corner from 25 yards.

Birmingham rarely threatened, and Mario Balotelli doubled the hosts' lead just before the break with a low strike across goal.

Roberto Mancini's side continued to dominate after the break, but couldn't add to their tally.