The qualified electors of a municipality may, by majority vote at a general election, as defined in s. 97.021, increase millage above those limits imposed by s. 200.081 in a referendum called for such purpose by the governing body of the municipality, but the period of such increase may not exceed 2 years. Such referendum also may be initiated by submission of a petition to the governing body of the municipality containing the signatures of 10 percent of those persons eligible to vote in such referendum, which signatures were affixed to the petition within 60 days prior to its submission.