The website of the Swedish prosecutor's office pursuing WikiLeaks founder Julian Assange has come under cyber attack in the latest salvo by his online supporters.

PandaLabs, the malware detection laboratory for computer security firm Panda Security, said the prosecutor's website, aklagare.se, was brought down yesterday by members of the "cyber hacktivist" group called "Anonymous."

Attempts by AFP to connect to the aklagare.se website around 5:00 pm (local time) were unsuccessful.

The attack on the Swedish prosecutor's website came as Assange was refused bail yesterday by a British judge over charges of sex crimes in Sweden.

Sean-Paul Correll, a threat researcher at PandaLabs, said the group called Anonymous launched the attack on the Swedish prosecutor's website and others against PayPal and the Swiss Post Office bank.

PayPal blocked financial transfers to WikiLeaks last week while the Swiss Post Office bank closed accounts held by Assange, whose release of secret US diplomatic cables has sparked an international furor.

PostFinance.ch, the website of the Swiss Post Office bank, was unavailable yesterday after coming under cyber attack.

PayPal's official blog, ThePayPalBlog.com, came under distributed denial of service, or DDoS, attack on Saturday and went down briefly but was back up yesterday.

In a classic DDoS attack, a "botnet" of zombie computers, machines infected with viruses, are commanded to simultaneously visit a website, overwhelming its servers, slowing service or knocking it offline completely.

Correll, the PandaLabs researcher, said on his blog that the Swedish prosecutor's website went down "instantaneously" with "over 500 computers in the voluntary botnet attacking the site all at once."

Correll said the website used by Anonomyos, anonops.net, has been the target of cyber attacks as well and went down temporarily yesterday.

WikiLeaks itself has been under cyber attack since Assange began releasing the US documents last week, forcing it to change addresses and servers. (AFP)