MILAN, April 11 (Reuters) - Up to three million customers of Italy's Banca Sella and its digital bank Hype have been unable to access their accounts online this week due to disruption which the regional lender said was caused by an IT update provided by Oracle.

Banca Sella said on Thursday the outage was not related to cybersecurity issues and does not affect other banking services such as the use of payment cards.

Cash transactions and payments can be made at Sella branches which will have extended opening hours to 6 p.m. (1600 GMT) until the incident is resolved, it added.

Banca Sella has around 1.3 million customers. Hype, which is a joint venture with the challenger bank illimity, has around 1.7 million customers.

"Our technicians are working with Oracle, which has been the supplier of the Sella Group's operating system for more than 20 years, to restore full functionality," Banca Sella said in an online statement.

"Several steps have been taken, but at the moment, the situation is still not back to normal," it added, saying it was unable to say when full online services would be restored.

Oracle had no immediate comment.

(Reporting by Gianluca Semeraro Editing by Keith Weir)