North Korea freed a Canadian pastor serving a life sentence on humanitarian grounds, the official KCNA news agency said on Wednesday, just hours after the United States warned it would counter any threat from the North with "fire and fury."There was no clear connection between the release of Hyeon Soo Lim and the heightened rhetoric between Washington and Pyongyang. Canadian officials said on Tuesday a delegation led by the country's national security adviser had gone to North Korea to discuss Lim's case.