United sensationally led 3-0 after a remarkable first half in which Wayne Rooney struck twice, Danny Welbeck added another and City captain Vincent Kompany was sent off.
City hit back after the break through Aleksandar Kolarov and Sergio Aguero but United, for whom Paul Scholes came out of retirement, held on to end City's cup defence at the first hurdle.
Source: PA
Source: PA