The council shall have power to levy and collect taxes on all taxable property, real and personal, within the limits of said corporation, not exceeding two per cent per annum upon the assessed valuation thereof, for general purposes, unless a greater amount of tax is authorized at an annual or special election, and to levy, assess and collect special taxes or assessments according to law, for local purposes or improvements; and to enforce the payment of such taxes and assessments in any manner to be prescribed by ordinance, not repugnant to the Constitution and laws of the United States or of this state.