British police are continuing to look for the WikiLeaks founder, Julian Assange, over rape allegations made against him in Sweden.

The Serious Organised Crime Agency, which is handling the case, confirmed yesterday it had flagged up an Interpol "red notice" to all UK police forces that the whereabouts of Assange were being sought.

Police sources said Assange would be arrested if they discovered his precise location. The 39-year-old is believed to be in the UK.

A Soca source said: "If there is intelligence or information to say he is in a said location, then that will be acted upon. With a red notice issue it means he's on the radar, on police force systems. Law enforcement Plc is looking for him."

A source close to Assange told the Guardian that his lawyer had been assured by police that he would be approached first if there was any attempt to detain the WikiLeaks founder.

Although the red notice does not amount to an arrest warrant, an Interpol spokesman said that often they were interpreted as a "valid request for provisional arrest" especially if the two countries, such as Sweden and the UK, have extradition treaties.

A Soca source described it as an "initial locate and trace" request by Interpol for Assange, with the red notice asking people to contact police if they have any information about his whereabouts.

Assange, who is from Australia and is thought to have been in London recently, moves regularly from country to country and is known to have spent periods in Britain and Sweden. The source added that police had not received any information relating to the whereabouts of Assange or any indication that he might currently be in the UK.

The red notice concerning Assange was sent from Interpol on 20 November to all its 188 member countries after being contacted by the Swedish authorities who want to interview him over sex offence allegations.

Assange is wanted by Swedish prosecutors on suspicion of rape, sexual molestation and unlawful coercion. He denies the allegations.

Initially details of the notice were marked "restricted" and only came to light yesterday after Sweden said its request could be publicised.

Today, Assange's lawyer issued a vigorous condemnation of the Interpol move. Comparing the Swedish prosecutor to Lavrentiy Pavlovich Beria, Stalin's notorious security chief, Mark Stephens said "neither Mr Assange nor his lawyers have been provided any further information beyond that reported in the press."

He continued: "This appears to be a persecution and a prosecution. It is highly irregular and unusual for the Swedish authorities to issue a red notice in the teeth of the undisputed fact that Mr Assange has agreed to meet voluntarily to answer the prosecutor's questions. Mr Assange has repeatedly sought meetings with the prosecutrix – both in Sweden and subsequently – in order to answer her questions and clear his name. It is relevant that Mr Assange sought permission from the prosecutrix to leave Sweden and she gave him her permission. Since leaving Sweden Mr Assange has continued to seek meetings with the prosecutrix, but his requests have either been ignored or met with a refusal."

He added: "At this point in time, we have no evidence pointing to a link between these allegations from August and the issue of the Interpol alert just two days after the WikiLeaks first release of US diplomatic cables. However, it is highly unusual for a red notice warrant to be issued in relation to the allegations reported as having been made, since Swedish law does not require custodial orders in relation to the allegation – indeed to our knowledge this is a unique action by the Swedish prosecuting authorities in applying for a red notice on the basis of these allegations.

"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."

If Assange is arrested in the UK, police will notify Swedish authorities immediately before he faces proceedings to extradite him to Sweden at City of Westminster magistrates' court in central London.

"Once he has been located, the Swedish authorities would be contacted and then they would send an arrest warrant and that gets processed by us, to make sure it ticks all the boxes within the legislation, and then it gets actioned," said the Soca source.

He said the process could be delayed if Assange chose to appeal against attempts to extradite him.

An Interpol spokesman said: "In cases where arrests are made based on a red notice, these are made by national police officials in Interpol member countries."

The WikiLeaks founder is facing growing legal problems around the world after US Republicans revealed yesterday they were pushing for his criminal prosecution under the Espionage Act.

Scotland Yard refused to divulge any discussions that may have taken place concerning Assange.

A Metropolitan police spokesman said: "We don't discuss purported communications regarding extradition cases unless someone is being called before the City of Westminster magistrates court, where we deal with our cases."

Meanwhile, Assange's mother, Christine, who runs a puppet theatre in Queensland, Australia, said she was worried about her son's wellbeing.

"He is my son and I love him, and obviously I don't want him hunted down and jailed. I'm reacting as any mother would. I'm distressed," she told Australian radio. "