US Secretary of State Hillary Clinton on Thursday warned Internet firms to avoid offering the "tools of oppression" to authoritarian Middle East regimes trying to crush democracy protests.

Clinton urged private companies to "embrace (their) role in protecting Internet freedom" and ensure protection of ordinary people as well as political activists.

Speaking at an Internet conference in The Hague, the chief US diplomat cited cases where "companies' products and services were used as tools of oppression," without naming the companies.

"I'd like to discuss three specific challenges that defenders of Internet freedom must confront," Clinton told delegates from more than 20 countries, non-governmental organisations, as well as cyber activists and bloggers.

"The first challenge is for the private sector to embrace its role in protecting Internet freedom," Clinton said, adding "in recent months we've seen cases where companies' products and services were used as tools of oppression."

Companies have also reportedly turned over sensitive information to governments about dissidents or shut down social networking accounts of activists involved in a political debate, she said.

"Today's news stories are about companies selling the hardware and software of repression to authoritarian governments," she told the Google-sponsored gathering.

"When companies sell surveillance equipment to the security agency of a Syria, or Iran, or in past times Gaddafi, there can be no doubt that it will be used to violate rights."