Tuscany's bailed-out Monte dei Paschi had unexpectedly launched a 13-billion-euro all-share takeover proposal for Mediobanca.

Italian bank Mediobanca on Tuesday rejected a takeover offer by state-backed rival Monte dei Paschi di Siena , saying a tie-up would be detrimental to its shareholders because it lacked any strategic and financial rationale.

Mediobanca rejected a 13.3 billion-euro takeover attempt by Monte dei Paschi, citing a lack of industrial logic and potential shareholder value destruction. The bid aimed to create Italy's third-largest bank with significant synergies.