Annitta Stenning, the City of Winnipeg's top civil servant, resigned unexpectedly Friday afternoon.

Neither city officials nor Stenning has offered an explanation for the chief administrative officer's sudden departure.

Mayor Sam Katz was not immediately available for comment.

In a statement issued Friday afternoon, Katz said he has accepted Stenning's resignation from the position of chief administrative officer based on "mutually agreeable terms."

Katz has appointed Alex Robinson to take over interim duties as CAO, effective immediately, the release said.

The Harvard grad has been employed by the city since 1991 in a number of roles, including vice-president of planning and development and manager of business liaison.

Appointment 'terrifying': councillor

Coun. Jenny Gerbasi told CBC News she was stunned by the news and disturbed by the appointment of Stenning's replacement.

"The person who has been appointed acting CAO is actually in charge of the EPC secretariat, which is political staff, so now we've gone from having an administrative leader in charge of all the departments to having a political appointee in charge of the entire City of Winnipeg," said Gerbasi, councillor for Fort Rouge - East Fort Garry.

"To me, that's really terrifying."

Winnipeg is currently in the process of hiring a new police chief; the CAO will make the final decision on the hiring.

Stenning was appointed in September 2003 to the city's top position, which reports to the executive policy committee (EPC), considered the mayor's cabinet.

Before being appointed CAO, Stenning spent four years as the first president and CEO of CentreVenture, Winnipeg's downtown development agency.