The United States will issue a formal diplomatic note to China expressing concern about cyber attacks that hit Google and dozens of other companies, and that researchers say originated in that country.

"We will be issuing a formal demarche to the Chinese government in Beijing on this issue in the coming days, probably early next week," US State Department spokesman P.J. Crowley told reporters Friday. "It will express our concern for this incident and request information from China as to an explanation of how it happened and what they plan to do about it."

The attack on Google targeted its intellectual property and the Gmail accounts of human rights activists protesting Chinese policies, the search giant said Tuesday. Google said 20 other firms were similarly hit by the "highly sophisticated and targeted attack," a number independent security researchers have raised to 34.

On Thursday, Microsoft said a previously unknown vulnerability in its Internet Explorer browser was used to penetrate Google's defenses, confirming findings provided by anti-virus firm McAfee. While there is no conclusive proof the attackers had formal ties to China, the sophistication and coordination of the assaults, combined with IP addresses used for many of the command and control channels, strongly suggest a state-sanctioned campaign from China, several researchers have said.

On Thursday, the deputy assistant secretary of State for East Asia and the Pacific met with the Chinese Embassy's deputy chief of mission in Washington to express concern and ask questions, according to Bloomberg News. He didn't receive any answers.

The news service went on to report that Google representatives briefed the Obama administration before it disclosed the attacks and announced it planned to stop filtering search results inside China. Google didn't seek US government support and administration officials didn't encourage or argue against proceeding. ®