British Foreign Secretary William Hague issued a warning on Tuesday to countries that try to restrict Internet freedom as he opened a global conference designed to set up cyberspace "rules of the road".

Government officials, technology firms, NGOs, bloggers and security experts from more than 60 countries are at the two-day talks in London, although the main speaker, US Secretary of State Hillary Clinton, pulled out at the last minute.

In his opening speech to delegates including those from Russia and China, Hague said the social and economic benefits of the Internet were immense and warned that any states that sought to block online activity would lose out.

"We must aspire to a future for cyberspace which is not stifled by government control or censorship, but where innovation and competition flourish and investment and enterprise are rewarded," the foreign secretary said.

Hague warned that human rights, particularly the right to privacy and freedom of expression, "should carry full force online".

"We reject the view that government suppression of the Internet, phone networks and social media at times of unrest is acceptable," he said.

Although he is likely thinking of protests in the Middle East and North Africa, British Prime Minister David Cameron himself mooted the idea of stopping rioters communicating via social media during unrest in England in August.

And William Echikson, Google's head of free expression in Europe, the Middle East and North Africa, warned at a side meeting in London that efforts to restrict online activity were not simply confined to undemocratic regimes.

Freedom of expression "is being challenged closer to home here in Europe. There are some 60 countries which impose controls now on the Internet, and that's up from two a decade ago," Echikson said.

"The dangers are really here in the present and they are threatening companies like Google," Echikson said.

Hague said the aim of the London talks would be to set up some basic global principles for cyberspace, including the need for universal access to the Internet and the need for governments to act "proportionately".

"In the place of today's cyber free-for-all, we need rules of the road," he said, adding that Hungary had agreed to hold a follow-on conference in 2012, and South Korea would hold another similar meeting in 2013.