WikiLeaks founder Julian Assange said that he was the target of an aggressive US investigation and feared extradition to the United States was "increasingly likely."

The 39-year-old Australian computer expert, whom Swedish authorities want to question over alleged sexual offences, has angered the US by releasing secret diplomatic cables on his website and teaming up with newspapers around the globe to amplify the impact of the disclosures.

Speaking to reporters from the grounds of the English country house where he was sent after his release on bail this week, Assange gave no hint of what charge he might face.

He denounced what he called a smear campaign against him and said he expected more attempts to tarnish his name.

"The risk we have always been concerned about is onward extradition to the United States and that seems to be increasingly serious and increasingly likely," Assange told reporters in the sprawling grounds of the house in eastern England where he must spend Christmas and New Year.

Asked if he was facing a US conspiracy, Assange told reporters: "I would say that there is a very aggressive investigation. A lot of face has been lost by some people, and some people have careers to make by pursuing famous cases."

US Attorney General Eric Holder has said his government was considering using the US Espionage Act, under which it is illegal to obtain national defense information for the purpose of harming the United States, as well as other laws to prosecute the release of sensitive government information by WikiLeaks.

One key question for US prosecutors is if they can determine whether Assange collaborated with the US Army intelligence analyst who is suspected of leaking the classified material. Assange has denied any connection with the former U.S. Army Specialist Bradley Manning.

Assange has described the curbs on him as "hi-tech house arrest." As part of his bail conditions, he must stay at the 18th-century mansion owned by former British army officer Vaughan Smith, situated close to the city of Norwich, around three hours' drive from London.

Assange gave reporters a double thumbs-up sign when he reported to a police station in the nearby town of Beccles. A daily visit to the police is one of the terms of his bail.

Host Smith has said that the Internet connection at the 10-bedroom house is not good. Assange, who must abide by a curfew and wear an electronic tag, said the conditions were "a gross impediment to my work" but would not stop him.

Despite the restrictions, he joked that he was enjoying the chance to have a Martini and snowball fight with friends after nine days in jail. Assange walked free from a London court on Thursday, freed on 200,000 pound ($312,500) bail.

Assange is accused of having unprotected sex with one woman in Sweden, and engaging in sex with another woman while she was sleeping in August.

He said he expected further attempted smears from the Swedish authorities but did not elaborate.-Reuters