Police say they have arrested four suspected hackers allied to the loose-knit Anonymous movement in connection with attacks on Spanish political party websites.
A National Police statement said two servers used by the group in Bulgaria and the Czech Republic have been blocked.
It said the four included the alleged manager of Anonymous' computer operations in Spain and Latin America, who was identified only by his initials and the aliases "Thunder" and "Pacotron."
The four are suspected of defacing websites, carrying out denial-of-service attacks and publishing data on police assigned to the royal palace and the premier's office online.
Tuesday's statement said the arrests were part of an Interpol operation.
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