LONDON - Skirmishes raged across cyberspace yesterday between WikiLeaks supporters and the companies they accuse of trying to stifle the group, with websites on both sides of the battle line taken out of service or choked off by attacks.

The U.N.'s top human-rights official raised the alarm over officials' and corporations' moves to cut off WikiLeaks' funding and starve it of server space - something she described as "potentially violating WikiLeaks' right to freedom of expression."

Navi Pillay also expressed surprise at the scale of the online attacks that have targeted major American financial players - in some cases denying access to their websites for hours at a time.

"It's truly what media would call a cyber-war. It's just astonishing what is happening," Pillay told reporters in Geneva.

Many U.S.-based Internet companies have cut their ties to WikiLeaks, including MasterCard Inc., Visa Inc., Amazon.com, PayPal Inc. and EveryDNS. Those moves have hurt WikiLeaks' ability to accept donations - and touched off a bout of Web-based warfare.

Retaliatory attacks - which WikiLeaks says it does not sanction - have been claimed by a loose-knit group of "hacktivists."