Cyber activists striking at companies seen as enemies of WikiLeaks tried to block the website of online payment firm Moneybookers on Friday but denied their campaign was intended to damage economic activity.

Some campaigners communicating on Internet channels also called for attacks on official Dutch websites following the arrest in The Hague on Thursday of a 16-year-old boy suspected of involvement in the online campaign.

A string of U.S. institutions has ended services to WikiLeaks after the website published thousands of secret U.S. diplomatic reports that have caused tension between Washington and several of its allies.

The attack on Moneybookers appeared to have blocked the site for about two minutes at about 1235 GMT but it subsequently came back online. The activists promised to continue their assault and cited Interpol's site as a possible target.

If we don't panic, and we get bigger, no one can stop us, wrote a participant in a chat room used by what the activists call the Operation Payback campaign.

In a statement, Moneybookers confirmed its website had been unavailable for a few minutes but the service was back up.

In light of recent events, we have been tightening security and applying additional vigilance which means that despite the attacks we continue to provide our service to users and merchants 24/7, it said.

The activists, who collectively call themselves Anonymous, said in a statement they were not hackers but rather average Internet Citizens.

We do not want to steal your personal information or credit card numbers. We also do not seek to attack critical infrastructure of companies such as MasterCard, Visa, PayPal or Amazon, the statement said.

SYMBOLIC ACTION

The point of Operation Payback was never to target critical infrastructure of any of the companies or organizations affected. Rather than doing that, we focused on their corporate websites, which is to say, their online 'public face'.

It is a symbolic action, it said.

Online retail and web-hosting powerhouse Amazon stopped hosting WikiLeaks' website last week, and on Thursday it briefly became the main target of the pro-WikiLeaks campaigners -- before they admitted it was too big for them, for the moment.

The Anonymous statement added that a lack of firepower was not the only reason the attack on Amazon had not succeeded. It felt attacking a major online retailer when people are buying presents for their loved ones, would be in bad taste.

Activists said Moneybookers had became a target because it had informed WikiLeaks in August it had closed its account with the service to comply with investigations by several governments into possible money laundering and other matters.

The Anonymous statement followed one by WikiLeaks which said the website had no links to the cyber attacks, and neither supported nor condemned them. The statement quoted WikiLeaks spokesman Kristinn Hrafnsson as saying the attacks were a reflection of public opinion on the actions of the targets.

Some freedom of information campaigners sympathetic to WikiLeaks look askance at the attacks, saying its cause cannot be furthered by denying freedom of information to others.

The teenage boy in the Netherlands was arrested by a high-tech crime unit after admitting to attacks on the websites of two credit card companies, MasterCard and Visa, the prosecution in the Netherlands said on its website.

THE GAME HAS CHANGED

The boy, whose details were not disclosed, was due to appear in court in Rotterdam on Friday afternoon.

On an online chat service used by the campaign, participants debated whether to end the attacks and focus instead on discovering more embarrassing material in the leaked documents.

We have at best given them a black eye. The game has changed. When the game changes so must our strategies, read a suggestion which proposed Operation Leakspin.

The idea would be to get hold of unreported stories buried in the thousands of cables and post snippets of them all over the Internet, the participant said.

(Additional reporting by Georgina Prodhan in London, Marius Bosch in Johannesburg)

(Writing by William Maclean; editing by Philippa Fletcher/ David Stamp)

Wikileaks Target