The foundation said in a statement Fintech, a U.S.-based investment fund owned by Mexican businessman David Martinez, had bought a 4.5 percent stake.

BTG Pactual Europe, a unit of the Brazilian investment bank controlled by billionaire financier André Esteves, purchased the remaining 2 percent.

The shares were sold at a price of 0.2375 euros per share. The bank's stock rallied 10.6 percent to 0.28 euros by 0824 GMT (9:24 BST).

The statement said the two buyers and the Monte dei Paschi foundation had committed to keeping a combined stake of 9 percent in the bank before and after a 3 billion euro capital increase due to be launched at the end of May.

Monte paschi top investor says sold 4.5 pct stake in bank to fintech advisory Monte paschi top investor says sold 2 pct to btg pactual europe Monte paschi top investor says sold shares in bank for 0.2375 euros per share Monte paschi top investor says signed shareholder agreement with buyers to help stability in shareholder structure Shares in monte paschi up 8.43 pct after share sale announcement

(Reporting by Silvia Aloisi)