Three suspected computer hackers who allegedly belong to a loose-knit international activist group that hacked into New Zealand Government websites, have been arrested in Spain.

Spain's National Police said today the three detainees were leaders of the Spanish section of a group that calls itself ''Anonymous'' and has attacked corporate and government websites around the world - New Zealand included.

The Associated Press reported police said a computer server in one of their homes was used to co-ordinate and carry out the cyber attacks on targets including two major Spanish banks, the Italian energy company Enel and the governments of Egypt, Algeria, Libya, Iran, Chile, Colombia and New Zealand.

New Zealand's Parliamentary Service suffered website outages last month after threats from ''Anonymous'', protesting against changes to copyright law.

That attack and others have led the Government to set up a new cyber bodyguard to protect high-risk government agencies from attacks by cyber spies and criminals.

The National Cyber Security Centre, announced by Communications and Information Technology Minister Steven Joyce this week, will also take on the functions of the Centre for Critical Infrastructure Protection, which helps protect critical national infrastructure such as the computer networks of banks and power companies.

Mr Joyce said the centre would be larger than the CCIP but its establishment would be funded from the existing budget of the Government Communications Security Bureau.

He said the Government was aware of ''a variety of cyber threats to New Zealand interests'' but he could not give details for reasons of national security.

The centre will be part of a new cyber-security strategy that includes a consumer education programme with organisations such as Netsafe.

The Spanish police statement said the only other countries to act against ''Anonymous'' so far are the United States and Britain. It attributed this what it called complex security measures that members use to protect their identity.

The suspects in Spain were arrested in Barcelona, Valencia and the southern city of Almeria, the statement said without specifying when the detainees were picked up.

Since October 2010, Spanish police specialising in cyber crime have analysed more than two million lines of online chat and Internet pages until they finally zeroed in on the three suspects. Their names were not given.

In January, British police arrested five young males on suspicion of involvement in cyber attacks by Anonymous, which has backed WikiLeaks.

''Anonymous'' has claimed responsibility for attacking the websites of companies such as Visa, Mastercard and Paypal, all of whom severed their links with WikiLeaks after it began publishing its massive trove of secret US diplomatic memos.

''Anonymous'' accused the companies of trying to stifle WikiLeaks and rallied an army of online supporters to flood their servers with traffic, periodically blocking access to their sites for hours at a time.

And in February, an Internet forum run by ''Anonymous'' directed participants to attack the websites of the Egyptian Ministry of Information and the ruling National Democratic Party.

In a Twitter post, the group claimed credit for taking down the ministry's website and said the group was motivated by a desire to support Egyptian pro-democracy protesters.