American International Group, the world's largest insurer, has announced the resignation of its chief operating officer Donald Kanak, who cited personal reasons for his departure.

AIG also said it appointed recently retired Citigroup president and chief operating officer Robert Willumstad and former Estee Lauder CEO Fred Langhammer to its board. The insurer offered no explanation for the departure, effective from the end of January.

AIG was involved last year in an accounting scandal which saw the resignation of its chairman, Maurice Hank Greenberg.