McDonald's Corp said its president and chief executive officer Charlie Bell, who has been battling cancer, has stepped down effective immediately.

Vice-chairman Jim Skinner has been elected CEO and a member of the company's board.

Mike Roberts, currently CEO of McDonald's USA, was named president and COO and a board member.

The fast-food group's chairman, Andrew McKenna, said in a company statement that Bell has resigned to "devote all of his time and energy to his courageous battle against cancer." McKenna called Bell a "remarkable leader" and said the board fully understood and respected his decision.

Bell has been battling colorectal cancer since spring. He returned to the hospital in August and again in September to clear up blockages caused by scar tissue from the surgery.

He was promoted to the top post at McDonald's on April 19 following the sudden death of then-chairman and CEO Jim Cantalupo from a heart attack.