MADRID, Oct 7 (Reuters) - Spain's Unicaja and Liberbank kicked off formal merger negotiations on Wednesday, after choosing advisors, Unicaja said.

Unicaja hired Uria Menendez as legal advisers, Mediobanca as financial advisers and Price Waterhouse Coopers as the auditor to undertake due diligence. A source with knowledge of the matter said that Liberbank’s board had hired Deutsche, Ramon y Cajal and Deloitte. (Reporting by Clara-Laeila Laudette)