The logo of Citi bank is pictured at an exhibition hall in Bangkok, Thailand, May 12, 2016.
Job cuts and structural changes at Citigroup Reuters / Athit Perawongmetha

Citigroup has begun announcing layoffs and implementing changes in the bank's plan to simplify its corporate structure.

More than 300 senior manager roles will be eliminated in the plan, Bloomberg reported, without identifying its sources.

"Today, we shared with our colleagues the next layer of changes across many of our businesses and functions as we continue to align Citi's organizational structure with our new, simplified operating model," the bank said in a statement Monday. "As we've acknowledged, the actions we're taking to reorganize the firm involve some difficult, consequential decisions, but we believe they are the right steps to align our structure with our strategy and ensure we consistently deliver excellence to our clients."

Reuters reported earlier, citing five people familiar with the situation, that the layoffs and management changes would start Monday and could affect thousands of employees.

Chief Executive Officer Jane Fraser started in September the reorganization of the bank's structure, with five units reporting directly to her.

"The new, flatter structure elevates the leaders of Citi's five businesses and eliminates management layers, which will speed up decision making, drive increased accountability and strengthen the focus on clients," the bank said at the time.

The third-largest U.S. bank will provide an update on organizational changes when it reports its fourth-quarter results in January.

"When completed, we will have a simpler firm that can operate faster, better serve our clients and unlock value for our shareholders," Fraser said in the latest earnings statement, on Oct. 13, in reference to the changes.