ROME, May 26 (Reuters) - Italian financial group Unipol said on Wednesday its UnipolSAI insurance unit had bought a stake of around 4% in regional bank Popolare di Sondrio. Unipol is the top investor in Italy’s fifth-largest lender BPER Banca and analysts say the move on Popolare di Sondrio has strategic implications for the banking sector’s ongoing consolidation process. UnipolSAI paid a price of 4.15 euros a share after saying late on Tuesday it would buy an up to 6.6% stake in Popolare di Sondrio, paying a premium of between 2% and 4% on the stock’s closing price of 4.008 euros. Unipol already owns 2.9% of Popolare di Sondrio and the share purchase brings its overall holding to 6.9%. Shares in Popolare Sondrio were up 5.8% in early trade. (Reporting by Giulia Segreti; editing by Valentina Za)