The international online vigilante group "Anonymous" has taken revenge for the arrest of three of its hackers by blocking the web site of the Spanish police, officials said.
"During the night of Saturday to Sunday at 2:00am, the police web site was the victim of an attack and was blocked for several minutes," a police source said Monday.
"Anonymous" claimed responsibility in a Twitter message on @Anon_Central, saying "Target: www.policia.es status: DOWN, for arresting peaceful protesters".
Spanish police announced Friday that three hackers from Anonymous had been arrested for online attacks on Sony PlayStation's online store and on the governments of Egypt, Libya and Iran among others.
It said the trio were suspected leaders of the Spanish operations of Anonymous, a so-called "hacktivist" group that breaks into computers online to pursue an agenda of political activism.
They were accused of launching "denial of service" (DDOS) attacks in which hackers infect computers worldwide and command them to link simultaneously to a targeted web site, swamping the site's servers and making it crash.
In a statement on the Internet, Anonymous denied they had any leaders at all.
"Greetings Spanish Government," it said.
"We know you have heard of us; We are Anonymous. It has come to our attention that you deemed it necessary to arrest three of our fellow anons, ... who you claim to be the leaders of Anonymous and for their participation in DDoS attacks against various websites...
"First and foremost, DDoSing is an act of peaceful protest on the Internet. The activity is no different than sitting peacefully in front of a shop denying entry. Just as is the case with traditional forms of protest...
"Regardless of how many times you are told, you refuse to understand. There are no leaders of Anonymous. Anonymous is not based on personal distinction..."
Police said one of the three suspects arrested, aged 31, had a server at his home in the northern city of Gijon to direct attacks on government, financial and business sites worldwide.
They are accused of hacking the Sony PlayStation online shop, the sites of major banks BBVA and Bankia, Italian power company Enel, and the governments of Egypt, Algeria, Libya, Iran, Chile, Colombia and New Zealand.
It is unclear if the suspects are accused of a role in the massive online attacks in April on Sony, which only this month restored PlayStation Network services everywhere except Japan, Hong Kong and South Korea.
The Internet vigilante group has denied carrying out the attack on Sony's online services, but said it could not rule out that some of its members were responsible.
The Spanish cell is also accused of attacking Spain's central election commission on May 18, four days ahead of regional elections, and later targeting both the Catalan police and the major UGT labour union.
Explore further: US Congress decriminalizes cellphone unlocking