The arrests in Barcelona, Alicante and Almeria involve suspects who allegedly had the ability to direct operations for Anonymous, the loosely affiliated hacking crew. Spanish police claim to have disrupted a key cell of the organisation. A server hosted in the Spanish city of Gijon was seized as part of these raids.
Investigators reckon the group is responsible for masterminding attacks on the Spain's Central Electoral Board (la Junta Electoral Central) last month as well as Sony's PlayStation Store. The group was also involved in attacks against government websites in Egypt, Algeria and Libya. Spanish police have already published, via Twitter, screensots from IRC logs that appear to show discussion of plans to attack the Spanish electoral board as well as Spanish police websites.
Source: The register