Any city, whether organized under the general laws of this state or by special charter or by constitutional charter, by vote of the constitutionally required percentage of the qualified electors thereof voting thereon, may incur an additional indebtedness for city purposes authorized in the charter of such city or by any general law of this state, not to exceed five percent of the taxable tangible property therein as shown by the last completed assessment for state and county purposes.
§ 95.120, RSMo