MADRID, May 10 (Reuters) - Spanish Telecom company Telefonica said on Monday it has agreed to sell four data centres to Nabiax, which had already bought 11 of its centres, in exchange for a 20% stake. The transaction includes four data centres in Spain and in Chile operating with a combined capacity of 9 megawatts, Telefonica said. Nabiax is a telecom infrastructure company that operates data centres in Spain and Latin America and is controlled by investment fund Asterion Industrial Partners. Nabiax was created after Asterion bought 11 data centres from Telefonica in 2019 for 550 million euros ($668.80 million). After the transaction announced on Monday, Asterion and co-investors will keep 80% in Nabiax. $1 = 0.8224 euros Reporting by Inti Landauro and Tomas Cobos, editing by Ed Osmond Our Standards: The Thomson Reuters Trust Principles.