The Department of National Defence says a high-altitude surveillance balloon has been detected over North American airspace and its movements are being tracked by NORAD.

The BBC says US defence officials are confident that the balloon belongs to China.

The balloon flew over the Aleutian Islands in Alaska, passed over western Canada, and later appeared in the skies over Montana.

The Department of National Defence says Canadians are safe and Canada is taking steps to ensure the security of its airspace.

DND says it is staying in frequent contact with American military officials as the situation develops.