HONOLULU, Hawaii, Jan 12, 2010 (AFP) - US Secretary of State Hillary Clinton called on Beijing Tuesday to explain cyberattacks originating from China against Google and at least 20 other firms.

Google earlier vowed to defy Chinese Internet censors and risk banishment from the lucrative market in outrage at "highly sophisticated" cyberattacks aimed at Chinese human rights activists.

"We have been briefed by Google on these allegations, which raise very serious concerns and questions," said Clinton in a statement issued while she was visiting Hawaii for talks with Japanese Foreign Minister Katsuya Okada.

"We look to the Chinese government for an explanation," the chief US diplomat added.

"The ability to operate with confidence in cyberspace is critical in a modern society and economy," she said.

"I will be giving an address next week on the centrality of Internet freedom in the 21st century, and we will have further comment on this matter as the facts become clear," the chief US diplomat added.

In San Francisco, Google said China-based cyber spies struck the Internet giant and at least 20 other unidentified firms in an apparent bid to hack into the email accounts of activists around the world.

The online espionage has Google reconsidering its business operations in China and it said it will no longer filter Internet search engine results in that country.

-AFP