Mark Wilson has stepped down as CEO of U.K.-based Aviva PLC, effective Oct. 9.

Wilson, who has been in the post since January 2013, was brought in to improve the British insurance group's financial performance and balance sheet strength.

"[G]iven the turnaround has been successfully completed, it is time for new leadership to take the group to the next phase of its development," Aviva said. The group remains on track to reach its target of operating EPS growth of more than 5% in 2018 and to achieve a dividend payout ratio of 55% to 60% of operating EPS by 2020.

Wilson will remain with the group until April 2019 to assist with an orderly transition.

Nonexecutive Chairman Adrian Montague will assume executive responsibilities during the transition period, subject to regulatory approval. He will lead a chairman's committee of the three executive directors — U.K. insurance CEO Andy Briggs, CFO Thomas Stoddard and international insurance CEO Maurice Tulloch — until a permanent CEO is named, after which Montague will revert back to his role as nonexecutive chairman.

The search for Aviva's new CEO will begin immediately, with internal and external candidates being considered. The process is expected to be completed within four months, the company said.