The cyber war between WikiLeaks supporters and companies refusing to do business with the whistle-blowing site intensified tonight, with fresh attacks threatened against Amazon and PayPal.
Anonymous, a loose-knit group of internet activists, has already disrupted the websites of companies including MasterCard and Visa by bombarding them with millions of bogus visits.
But the activist group's "Operation Payback" has also been hit, with Facebook and Twitter deleting their accounts.
Facebook said it deleted the Operation Payback account because it was promoting a 'distributed denial-of-service' (DDoS) attack.
Meanwhile, a WikiLeaks spokesman denied any connection with the "hacktivists" but described the attacks as a "reflection of public opinion".
In the real world, WikiLeaks' founder Julian Assange, who is on remand in London after being arrested and refused bail over sexual offence charges he is facing in Sweden, met his team of lawyers at Wandsworth prison this afternoon.
His solicitor, Mark Stephens, told the Guardian he was "quite chipper, he seemed to be bearing up".
Mr Stephens said Assange does not have access to a computer or the internet and added that he was concerned that "people have unjustly accused WikiLeaks of inspiring cyber attacks".
This afternoon a message on the Op-Payback Twitter account prompted fears of an attack on Amazon, reading: "TARGET: http://www.AMAZON.COM LOCKED ON!!!"
But subsequent posts appeared to show the target was in fact PayPal, with messages reading: "Everyone's attacking http://www.paypal.com."
A statement on the WikiLeaks website read: "WikiLeaks is aware that several government agencies and corporations, including the Swedish prosecutor, Mastercard, PayPal and State.gov, have come under cyber-attack in recent days, and have often been driven off-line as a result.
"The attacks are of a similar nature to those received - and endured - by the WikiLeaks website over the past week, since the publication of the first of 250,000 US embassy cables.
"These denial of service attacks are believed to have originated from an internet gathering known as Anonymous.
"This group is not affiliated with WikiLeaks. There has been no contact between any WikiLeaks staffer and anyone at Anonymous. WikiLeaks has not received any prior notice of any of Anonymous' actions."
Spokesman Kristinn Hrafnsson said: "We neither condemn nor applaud these attacks. We believe they are a reflection of public opinion on the actions of the targets."
Mike Prettejohn, a director of security firm Netcraft, which is monitoring the attacks, said: "They are all pretty difficult targets. Amazon has a huge infrastructure. It's a very technically sophisticated company.
"But we have already seen disruption at Visa and PayPal."
He said typical DDoS attacks used malware, or malicious software, to take advantage of vulnerable computers, adding: "This is more of a volunteer effort. It's open to more people and possibly for a longer period of time.
"Because of that it may be more difficult to defend against."
The US administration has put intense pressure on companies to cut ties with WikiLeaks, hurting its ability to accept donations.
Top UN human rights official Navi Pillay responded in Geneva today by saying she was concerned moves against WikiLeaks "could be interpreted as an attempt to censor the publication of information" in a way that violates the right to free expression.
Meanwhile, WikiLeaks' payment processor, DataCell, said it was preparing to take legal action against Visa and MasterCard over their refusal to process donations.
DataCell chief executive Andreas Fink said in a statement: "It is obvious that Visa is under political pressure to close us down. We strongly believe a world-class company such as Visa should not get involved in politics and just simply do their business where they are good at. Transferring money."
A number of posts attributed to Anonymous have appeared online, including a manifesto and letter of intentions.
In one blog post the group wrote: "Hello World. We are Anonymous. What you do or do not know about us is irrelevant. We have decided to write to you, the media, and all citizens of the free world at large to inform you of the message, our intentions, potential targets, and our ongoing peaceful campaign for freedom. The message is simple: freedom of speech."
DDoS attacks, which are illegal in the UK, involve overloading a website with high numbers of requests so it stops working. Anonymous said it was leading a "peaceful campaign" and denied being a terrorist or vigilante organisation.
The blog post continued: "Anonymous is doing what many successful campaigns have done in the past; a sit-in. It may be hard to comprehend, but a digital sit-in is our most effective method to show that all of us deserve freedom of speech and a free internet."
Facebook said: "We take our Statement of Rights and Responsibilities seriously and react quickly to reports of inappropriate or illegal content and behaviour.
"In this case, we removed a page because it was promoting a DDOS attack.
"The WikiLeaks page on Facebook does not violate our policies and remains up.
"We haven't received any official requests to disable it, nor any notification that the articles posted on the page contain unlawful content."
By 6pm more than 280,000 people had signed up to an online petition calling on the US Government and corporations to "stop the crackdown" on WikiLeaks.
PayPal General Counsel, John Muller, said the WikiLeaks account was reviewed after the receipt of a letter from the US Department of State "stating that WikiLeaks may be in possession of documents that were provided in violation of US law.
"We restricted the account based on our Acceptable Use Policy review. Ultimately, our difficult decision was based on a belief that the WikiLeaks website was encouraging sources to release classified material, which is likely a violation of law by the source.
"While the account will remain restricted, PayPal will release all remaining funds in the account to the foundation that was raising funds for WikiLeaks.
"We understand that PayPal's decision has become part of a broader story involving political, legal and free speech debates surrounding WikiLeaks' activities. None of these concerns factored into our decision."
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