Ottawa Mayor Jim Watson suffered a fractured pelvis during a "freak accident" while snowmobiling with other councillors in the rural riding of Osgoode.

In a letter to councillors, Watson's chief of staff Serge Arpin said the mayor was injured during a snowmobiling event in the rural community of Osgoode on Saturday afternoon.

Jim Watson has served as Ottawa's mayor since 2010, without absence. (CBC) Queensway-Carleton Hospital for treatment and released later on Saturday. Watson was taken to theHospital for treatment and released later on Saturday.

The letter states Watson will need between four and six weeks for a full recovery.

"It is likely that Mayor Watson will have to curtail his involvement in community events over the coming days and weeks," the letter said.

Mayor hit gas by mistake, councillor says

On Sunday, Coun. Mathieu Fleury said he witnessed Watson crash. Fleury said he, Watson and councillor Michael Qaqish were learning from their colleague, Osgoode Coun. George Darouze.

"The mayor had received training and had just decided to try it out and confused, what he describes as the brake and the power, and the incident happened where he rolled off the snowmobile," said Fleury, a trained lifeguard who administered emergency first aid to Watson.

The injury comes as the city's budget faces a final council vote on March 11.

Deputy Mayor Bob Monette told CBC News he hasn't been asked to step in but either he, the other deputy mayor Mark Taylor or Coun. Eli El-Chantiry can replace Watson to chair council meetings.

Ottawa last needed an acting mayor in 2009 when Larry O'Brien was forced to take a leave of absence.