Market analysts don't like what they're seeing in American International Group Inc.'s third-quarter results.

The insurer on Monday reported a net loss of $231 million compared with net income of $2.2 billion during the same period a year earlier.

“Compared to the prior-year quarter, the third-quarter net loss was primarily due to lower income on hedge fund investments and assets marked to fair value through earnings, lower realized investment gains and lower income from settlements of nonoperating litigation,” AIG said in a statement.

“The third-quarter 2015 earnings results were disappointing all around,” said Paul Newsome, managing director at Sandler O'Neill & Partners L.C. in Chicago in an investor note after the earnings report.

During a Tuesday conference call with analysts, AIG President and CEO Peter Hancock said the company plans to cut 23% of its 1,400 senior management employees in a restructuring.

“We need fewer generals on the field,” Mr. Hancock said.

Mr. Hancock also rejected investor Carl Icahn's call to split off the insurer's life and mortgage insurance units from its property/casualty business. Mr. Hancock said AIG management and directors had previously examined the issue and “concluded that it did not make financial sense.” He did add, though, that AIG would meet with Mr. Icahn to discuss the issue and later told CNBC the meeting would take place Thursday.

For the third quarter, net written commercial property/casualty insurance premiums fell 5.6% from the same period in 2014 to $5.20 billion. The combined ratio deteriorated to 102.7% from 102.1%.

For the first nine months of the year, net income fell 41.3% to $4.04 billion. Net written commercial property/casualty insurance premiums fell 3.0% to $15.83 billion while AIG's combined ratio deteriorated to 99.6% from 99.2%.

AIG said its restructuring initiatives will focus on organizational simplification, operational efficiency and business rationalization, which are expected to generate pretax annualized savings of approximately $400 million to $500 million when fully implemented.

“These initiatives are expected to result in pretax restructuring and other costs of approximately $0.5 billion including approximately $0.3 billion of employee severance and one-time termination benefits, concentrated initially among management's senior levels. Further staff reductions are anticipated in 2016,” AIG said in its statement.

Analysts saw problems with most aspects of AIG's third-quarter operations.

“The only segment that performed better than what we were expecting was mortgage guaranty, and only modestly so,” Mr. Newsome wrote. “Every other segment reported materially worse-than-anticipated results relative to what we were looking for as well as the same period a year ago.”

“This wasn't a good quarter,” said Mark Dwelle, an analyst at RBC Capital Markets L.L.C. in Richmond, Virginia, in a research note. While weak investment results were a “big factor,” the restructuring charge and ongoing reserve additions also “played a hand in the quarter's fairly poor results,” he wrote.

“Capital management was a clear bright spot and the mortgage unit did well, but this wasn't enough,” he added.

“We agree with what we expect is the broad consensus that AIG has a great global franchise, but that the company's operating performance is below its potential,” Cliff Gallant, an analyst at Nomura Securities International Inc. in San Francisco, wrote in a note.

He pointed out that outsiders “are pressing for the company's breakup and if the plan could overcome the hurdles related to the tax assets and (systemically important financial institution) standing while freeing up capital and reducing costs, these are certainly plans worth exploring. Ultimately, however, we view that AIG's main problem is solving the riddle of getting the underwriting performance right in a very tough market with well-run competitors. For this, we do not expect an easy fix.”