The 39-year-old Australian, who is thought to be in Britain, is wanted by Swedish prosecutors on suspicion of two counts of rape.
On Tuesday, Interpol issued a “red notice” to 188 countries, stating that Assange was wanted in Sweden and asking anyone with information about him to contact their local or national police force.
The notice has reportedly been brought to the attention of all British forces by the Serious Organised Crime Agency, which is handling the case. Assange’s precise location remains unknown but he is a frequent visitor to Britain. He conducted press conferences in London earlier this year and is reportedly in hiding near the capital.
While red notices do not amount to an arrest warrant, an Interpol spokesman said they were often interpreted as a “valid request for provisional arrest”, especially when the countries involved have an extradition treaty, as Sweden and Britain do.
A source at Scotland Yard said it has received no information about Mr Assange’s whereabouts. Mark Stephens, his British lawyer, said that he had not been contacted by either Interpol or police.
As the search intensified, the WikiLeaks website, which is releasing a selection of more than 250,000 classified US diplomatic cables, came under cyber-attack, making it inaccessible to users in the United States and Europe.
In a Twitter message, WikiLeaks said it was under a “distributed denial of service attack”, a method used by hackers to slow or bring down sites. The assault is believed to come from China.
The allegations against Mr Assange surfaced in August when two women went to police with complaints of sexual assault.
Stephens said on Wednesday that the red notice was a “persecution and prosecution” of his client, and that the Swedish authorities had ignored repeated requests from Mr Assange for a meeting.
He said: “It is highly irregular and unusual. Mr Assange has repeatedly sought meetings with the prosecutrix – both in Sweden and subsequently – in order to answer her questions and clear his name.
“We are also investigating whether the prosecutor’s application to have Mr Assange held incommunicado without access to lawyers, visitors or other prisoners – again a unique request – is in any way linked to this matter and the recent, rather bellicose US statements of an intention to prosecute Mr Assange.”
A spokesman for Scotland Yard refused to comment about Assange, but said: “If an arrest warrant has been issued of any kind to all forces around the world then those forces would act on any information they received.”
Assange’s mother, Christine, who runs a puppet theatre in Queensland, Australia, said she was worried about her son. She said: “Obviously I don’t want him hunted down and jailed. I’m reacting as any mother would. I’m distressed.” The Telegraph