LONDON — Julian Assange, the founder of the controversial WikiLeaks website, was arrested here Tuesday and ordered to remain in custody until a hearing next week on his possible extradition to Sweden, where he is wanted for questioning over allegations that he sexually assaulted two women.

The jailing of Assange came as governments and businesses around the world continued their efforts to halt the ability of WikiLeaks to function. On Tuesday, a Visa Europe spokesman announced the firm was suspending its business with WikiLeaks, following in the footsteps of Amazon.com, MasterCard, online pay service PayPal and others.

Assange’s lawyer, Mark Stephens, called his client innocent of any sex charges and questioned whether the accusations are part of an effort by governments to silence him. “”Many people believe Mr. Assange to be innocent, myself included,”” he said. “”Many people believe the prosecution to be politically motivated.””

Assange, 39, turned himself in to police Tuesday morning, hours after Britain received a formal warrant for his arrest from Swedish authorities. Assange denies any wrongdoing and says he will fight the attempt to extradite him, beginning with a hearing Dec. 14.

That could be the start of a legal battle that could drag on for weeks or even months, in part because the case against him in Sweden remains rather murky. Assange, who is Australian, is eager to avoid extradition for fear that it could set the stage for him to be sent to the U.S. if prosecutors there charge him with offenses relating to the WikiLeaks disclosures of State Department diplomatic cables and classified Pentagon files related to the wars in Iraq and Afghanistan.

Those leaked files have turned Assange into an international figure, vilified by the U.S. and governments around the world for spilling official secrets while lionized by activists demanding a free flow of information. In Washington, the Obama administration blames Assange for recklessly damaging U.S. relations with other countries and even aiding terrorists.

The ability of WikiLeaks to raise money and release information is being hemmed in as the businesses it relies on to operate terminate their relationships, saying the organization’s actions are in violation of customer agreements. A PayPal spokesman said a U.S. State Department letter Nov. 27, which termed as illegal WikiLeaks’ dissemination of the American diplomatic cables, “”triggered a review”” of a fundraising account on WikiLeaks website.

While businesses can act on their own, the U.S. government faces a high legal hurdle to trying to shut down the site through court action, said Marcia Hoffman, senior staff attorney for the electronic Frontier Foundation.

A spokesman for WikiLeaks, however, vowed that Assange’s arrest would not affect the website’s plans to continue publishing its cache of confidential documents. Among WikiLeaks’ strategies to keep its content available is so called “”mirroring”” — copying its files and documents to scores of other sites around the Web. As of Tuesday morning, WikiLeaks listed 755 mirror sites, more than twice as many as it said it had just two days earlier.

The sex accusations against Assange in Sweden have dogged him since the summer, before his organization began releasing portions of its huge trove of rifled State Department cables. The allegations stem from separate liaisons he had with two women in August, which Swedish prosecutors say may have involved molestation, “”unlawful coercion”” and rape.

Assange insists that the encounters were consensual. His lawyer, Stephens, characterizes the case as a “”dispute over consensual but unprotected sex.””

Stephens has denounced Sweden as “”one of the lickspittle states”” that have kowtowed to American demands in the past, particularly by assisting in the controversial practice of “”extraordinary rendition”” of terrorism suspects.

The lawyer also asserts that Assange has been willing from the start to cooperate with Swedish authorities in their investigation, but that his offers to submit to some form of questioning, both in Sweden while he was still in the country and later in London, were repeatedly rebuffed.

“”We are in the rather exotic position of not having seen any of the evidence (of the crimes) that Mr. Assange is accused of,”” Stephens told reporters after Tuesday’s preliminary hearing.

In a packed London courtroom Tuesday afternoon, Assange formally refused voluntary extradition to Sweden and asked to be released on bail. Throughout the hourlong hearing, Assange, in a dark suit, sat quietly in a glassed-in booth reserved for defendants.

Prosecutors objected to the bail request, saying that Assange’s nomadic lifestyle made him a flight risk. They noted that he first gave the court only a post office box as an address and, when that was disallowed, a street address in Victoria state in his native Australia.

The judge sided with the prosecution, despite the presence of several high-profile people willing to act as Assange’s bond guarantors, including the British filmmaker Ken Loach and socialite Jemima Khan, daughter of the late Anglo-French financier Sir James Goldsmith.

The case has been a somewhat tortuous one, with Swedish authorities disagreeing among themselves as to whether there were grounds to even pursue Assange for questioning. Last month, a court in Stockholm paved the way for a warrant to be issued against Assange, who by then was staying at an undisclosed location in Britain.

The first warrant apparently contained an error, which prevented British authorities from executing it until a corrected version was issued. The amended European arrest warrant was served Monday; by that evening, Stephens signaled that his client would turn himself in.

The warrant is an instrument that allows for quicker-than-usual extradition between European nations. If Assange is sent back to Sweden, and if authorities there decide enough evidence exists to prosecute him for sex crimes, he could face several years in prison if found guilty.

As yet, however, no formal charges have been filed.