Madrid, Spain (CNN) -- Police said Friday they had arrested the top three suspected leaders in Spain of the international computer hacker network called Anonymous, which is suspected of numerous cyber-attacks on Sony's PlayStation network and government and business websites.
Anonymous has gained international notoriety over the last several years for its computer-security attacks on major companies, including MasterCard and Visa and government websites for Tunisia and Egypt.
Sony Computer Entertainment president and America division chairman, Kazuo Hirai, sent a letter to the U.S. Congress last month saying that Sony had found a file that could link the attack against Sony to Anonymous.
The Spanish police said in a statement that their investigation began last October after Spain's Ministry of Culture's website was overloaded in a so-called denial of service attack, to protest Spanish legislation aimed at cracking down on illegal computer downloads.
The first arrest, of the three, came soon after a cyber-attack May 18 against a Spanish National Electoral Commission website just days before local and regional elections.
Police said they arrested a 31-year-old suspect in southern Almeria province and later seized from his home in the northern port city of Gijon a computer server that was used to coordinate and execute the attacks.
Soon after, attacks against the websites of the Spanish Parliament, the UGT trade union and the Catalan regional police led to the identification of two other suspects, who were arrested in Barcelona and Alicante, on Spain's eastern Mediterranean coast.
The police did not immediately provide further details about the suspects, nor did they specify to what extent the Spanish branch of Anonymous might have participated in the recent attacks on Sony's PlayStation.
Other targets of the Spanish branch, the police said, included the large Spanish banks BBVA and Bankia, the Italian energy firm ENEL, and government websites in Egypt, Algeria, Libya, Iran, Chile, Colombia and New Zealand.
In one of the locations searched, police found a large quantity of software programs specifically designed to infect third-party computers. The suspects encoded their communications and penetrated nearby secure Wifi networks, since two of the suspects did not even have an Internet connection at home, the police said.
Anonymous, formed in 2008, is set up with independent cells that share general objectives and support each other through promotional videos, chats and various networks, the police statement said.
It is the first arrest of alleged Anonymous participants in Spain, after similar arrests in the United States and Britain, the Spanish police statement said.