* Navi Pillay dismayed at reports of pressure on companies

* Says measures could be interpreted as attempt at censure

* Group case raises difficult issues requiring balancing act

(Adds background, quotes)

By Stephanie Nebehay

GENEVA, Dec 9 (Reuters) - U.N. High Commissioner for Human Rights Navi Pillay voiced concern on Thursday at reports of pressure being exerted on private companies to halt financial or Internet services for WikiLeaks.

Pillay said that taken together, the measures could be interpreted as an attempt to prevent WikiLeaks from publishing, thereby violating its right to freedom of expression.

While it was not clear who was behind the cyber attacks and counter-attacks, they raised concerns about the need for countries to protect the right to freely share information, as required under international law, she said.

“I am concerned about reports of pressure exerted on private companies including banks, credit card companies and Internet service providers to close down credit lines for donations to WikiLeaks, as well as to stop hosting the website,” she told a news conference.

“If WikiLeaks has committed any recognisable illegal act then this should be handled through the legal system, and not through pressure and intimidation including on third parties,” Pillay added, without elaborating.

Wikileaks has angered U.S. and other authorities by starting to release details of 250,000 confidential diplomatic cables.

Pillay noted that they included some documents pointing to U.S. officials being aware of widespread use of torture by Iraqi forces and nevertheless transferring detainees to Iraqi custody.

“The case raises complex human rights questions about balancing the freedom of information, the right of the people to know, and the need to protect national security or public order,” she said. “This balancing act is a difficult one.”

COURTS OF LAW

A landmark international treaty on civil and political rights protects the right to freedom of expression. Any restrictions placed on these freedoms must be both necessary and proportional, according to the former U.N. war crimes judge.

“Courts of law are equipped to address the delicate issue of balancing competing rights and values,” she said.

Pillay, referring to WikiLeaks founder Julian Assange, said: “If Mr. Assange has committed any recognisable offence then the judicial system, following fair procedures, should be able to address how these rights can be balanced.”

She noted the accusations against the 39-year-old Australian for sex crimes in Sweden, for which he was remanded in custody in Britain on Tuesday, are unrelated to the leaked information.

More cyber attacks in retaliation for attempts to block WikiLeaks website are likely in a “data war” to protect Internet freedom, a representative of one of the groups involved said on Thursday. [ID:nLDE6B8OUS]

The websites of credit-card giants MasterCard and Visa have already been brought down through distributed denial-of-service attacks that temporarily disable computer servers by bombarding them with requests.

“This is truly what media would call a cyber-war. It is just astonishing what is happening,” Pillay said. (Editing by Matthew Jones)