Italian bank Intesa Sanpaolo on Friday said an Italian investigation into a series of derivative trades involved "negligible" deals carried out in 2010 that have no impact on its accounts.

Prosecutors in the southern town of Trani are investigating derivatives contracts made by the country's three largest banks including troubled lender Monte dei Paschi di Siena , judicial sources said on Friday.

"Intesa Sanpaolo underlines that this investigation dates back to 2010 and regards the relations between subsidiary Banco di Napoli and some of its customers," the bank said.

"The Intesa Sanpaolo Group, as always, has offered investigating authorities utmost cooperation, with full confidence in their action," it said.

"The deals involved are negligible and have no material impact on the Group's financial statements", the bank said.

(Reporting by Antonella Ciancio, editing by Danilo Masoni)