Citigroup Inc. (NYSE:C), the third largest U.S. bank, on Tuesday reported a slight decline in third-quarter adjusted earnings on weak fixed-income trading revenue and a sluggish mortgage business.

The New York bank, which missed analysts' estimates, booked adjusted net income of $3.26 billion, or $1.02 per share, compared with $3.27 billion, or $1.06 per share, a year earlier.

Fixed-income revenue of $2.8 billion, excluding one-time events, decreased 26 percent from the prior-year period, "reflecting lower volumes and a more uncertain macro environment," the bank said in a statement.