"Both Andalusian clubs have reached an agreement today for the transfer of the defender Sergio Sanchez," Malaga said in an emailed statement.
"The player signed his new contract for the next four seasons and will be presented to the fans tomorrow in La Rosaleda Stadium," the club added.
Malaga did not disclose any financial details but local media reported they had paid 2.8 million euros for the 25-year-old, who has made a remarkable comeback after heart surgery last year.
Sanchez will join Argentines Diego Buonanotte and Martin Demichelis, Dutch duo Joris Mathijsen and Ruud van Nistelrooy, Spanish pair Joaquin and Nacho Monreal and French midfielder Jeremy Toulalan as new recruits at the club.
Malaga were bought by a member of the Qatari royal family at the end of the 2009/10 campaign.
After finishing 11th in La Liga last season they are building a squad for coach Manuel Pellegrini that they hope will challenge for a European qualifying berth next season.
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