By Valentina Za and Gianluca Semeraro MILAN (Reuters) -State-backed Monte dei Paschi di Siena on Friday joined the consolidation wave sweeping Italian banking with a surprise 13.3 billion euro ($14 billion) all-share offer to buy merchant bank Mediobanca.

Banca Monte dei Paschi di Siena SpA made a surprise offer to acquire larger rival Mediobanca SpA in a deal valued at €13.3 billion ($13.9 billion), adding a new twist in a series of takeover attempts that are shaking up Italy’s banking industry.

The deal intensifies with MPS offering 23 of its shares for every 10 shares of Mediobanca, representing a 5% premium over the last closing price.