The UN's human rights chief on Thursday expressed concern about pressure on private companies to stop providing financial or Internet services for whistleblower site Wikileaks.

"I'm concerned about reports of pressure exerted on private companies, including banks, credit card companies, to close down credit lines for donations to WikiLeaks as well as to stop hosting the website or its mother sites," said Navi Pillay, the UN High Commissioner for Human Rights.

"They could be interpreted as an attempt to censor the publication of information, thus potentially violating WikiLeaks' right to freedom of expression," she said at a press conference.

"If WikiLeaks has commited any recognisable illegal acts then this should be handled through the legal system and not through pressure and intimidation including on third parties," she said.