Upon receiving the petition and recommendation of the city planning commission, or upon its own motion, whenever the public peace, health, safety, comfort, convenience, interest or welfare may require, the council is authorized and empowered to determine the minimum distance back from the street line for the erection of buildings or structures along any portion of any street in the city, and to order the establishment of a line to be known and designated as a setback line, between which line and the street line no buildings or structures shall be erected or constructed.