BEIJING ? China declared its Internet "open" Thursday but defended censorship that has prompted web giant Google to threaten to pull out of the country, adding a potential new irritant in China-US relations.

But Google appeared to be winning the battle for hearts and minds, with Chinese online users flooding the web and visiting the company's Beijing offices to express support and urge the Internet giant not to leave China.

"The Chinese government administers the Internet according to law and we have explicit stipulations over what information and content can be spread over the Internet," foreign ministry spokeswoman Jiang Yu told reporters.

Jiang's comment marked China's most direct response yet after Google's shock announcement Tuesday that it would stop bowing to Chinese Internet censors and could pull out of the world's largest online market of 360 million users.

Google said the move was a protest against censorship and what it called "highly sophisticated" cyber attacks on its systems, which were aimed at Chinese human rights activists and believed to have originated in China.

China employs a vast system of web censorship dubbed the "Great Firewall of China" that blocks content such as political dissent, pornography and other information viewed as objectionable.

But at Google's offices in Beijing, dozens of supporters stopped by to voice their support, leaving messages, flowers and fruit.

"Goodbye Google. You can build the wall, but you can't separate the hearts of the people. We want to see the other side of the wall," said a message from one supporter.

"Freedom?" said another message in English and Chinese.

The Chinese spokeswoman Jiang declared the country's Internet "open" but declined to offer a detailed response to US Secretary of State Hillary Clinton's call for China to explain the alleged cyber attacks.

"I believe if there are some appeals for that, (authorities) will investigate it," Jiang said at the regular news briefing.

She refused to elaborate, and also refused to comment when asked repeatedly whether the purported attacks originated in China and were orchestrated by the government.

The issue was shaping up as the latest item on a growing list of disputes between China and the United States over trade, climate change and human rights.

State media said Chinese parliamentary leader Wu Bangguo told a group of visiting US senators the two sides should "respect each other's core interests and properly handle sensitive affairs," without specifically mentioning Google.

The statement by Wu -- nominally China's second-ranking political figure -- is typically used by Beijing to express displeasure about what they view as unwanted interference in Chinese affairs.

On Wednesday, White House spokesman Robert Gibbs confirmed that the Obama administration had held talks with Google. While declining to offer details, he stressed the United States backed the "right to a free Internet."

EU Competition Commissioner Neelie Kroes on Thursday expressed concern about Internet policy in China, underlining the importance of an open network.

However, a Chinese official said tight Internet controls were needed, saying the nation's online environment faced "severe challenges" as it grew and became more central to the nation's economy.

Wang Chen, head of the central government's information office, said in comments on the government's website that the nation must "strive to build a healthy, civilized, safe and orderly" Internet environment.

Such wording is usually employed to justify censorship.

Chinese Internet users flooded the web with messages of support for Google and the ideal of a free and open online environment.

"It?s not Google that?s withdrawing from China, it?s China that?s withdrawing from the world," one user said on Twitter, a sentiment echoed in other tweets. The micro-blogging site is currently blocked by Beijing.

An editorial in China's English-language Global Times newspaper said a Google departure would be a "setback to China and serious loss to China's Net culture."

Meanwhile, the Financial Times reported that the chief executives of Microsoft and Hewlett-Packard had declined to back Google's threat to pull out of China over censorship and cyber attacks.