By Andrea Mandala and Valentina Za MILAN (Reuters) -BPER Banca's CEO on Friday said its 4.3 billion euro ($4.5 billion) all-share takeover bid for smaller peer Banca Popolare di Sondrio was a defensive move prompted by a raft of merger proposals across Italy's banking industry.

Banca Popolare di Sondrio shares jumped Friday while BPER Banca shares slumped more than 8% on news of the bid.

Italian bank BPER said Friday that it has made a 4.3-billion-euro takeover bid for fellow lender Banco Popolare di Sondrio. Popolare di Sondrio sources said that the move had not been agreed on with them before being announced.

The latest unsolicited bid in Italian banking follows similar moves by UniCredit on Banco BPM and state-backed Monte dei Paschi di Siena (MPS) on Mediobanca. Unsolicited bids are historically rare in global banking, making Italy the exception.