When Yi Ran is working on new designs for his Yinshen Clothing company, he often turns to Google to search for pictures to use as inspiration. "The results are more complete and objective than Chinese search services," the 30-year-old from Guangzhou said.

But for the past two weeks, when Yi has tried to call up the U.S. search engine, it's been unavailable - as have a wide variety of other Google services, including Gmail, Google Books, Google Scholar and even country-specific search pages like Google.de, the company's German home page.

Chinese authorities have given no explanation for the disruption, which began about five days before the 25th anniversary of the crackdown on pro-democracy protesters that culminated June 4, 1989, at Tiananmen Square in Beijing. Certain Google services such as YouTube have been totally unavailable in China for years, and politically sensitive periods like the Tiananmen anniversary often bring intensified, if temporary, censorship of many foreign news websites and Internet search terms.

But experts said the current broad-based and prolonged disruption of Google offerings seems to be an escalated - and possibly long-term - crackdown on the Mountain View, Calif.-based Internet giant.

"It would be wrong to say this is a partial block. It is an attempt to fully block Google and all of its properties," said a founder of GreatFire.org, a well-known website that has been monitoring China's Internet censorship program since 2011. The founder said via phone that the site's administrators do not disclose their names publicly because of the sensitive nature of the content on their site. He would not reveal his real name, apparently fearing retribution.

So far, Google is taking a low-key approach. Spokesman Matt Kallman said the company had "checked extensively and there are no technical problems on our side" but refused to comment further. According to Google's Transparency Report, an ongoing update on worldwide service disruptions to the company's products, the slowdown in traffic from China began May 31.

Tensions between Beijing and Washington over cybersecurity have been escalating in recent weeks. Last month, the U.S. Justice Department formally charged five Chinese military officers with hacking into American companies and stealing trade secrets; China then said it would implement a security review on imported technology equipment.

Earlier this month, the state-run newspaper China Daily ran a story warning that companies like Google and Apple could pose a threat to Chinese users because of their cooperation with U.S. government surveillance activities. Those charges mirror warnings by American officials dating back several years that Chinese businesses, including Huawei Technologies Co. and ZTE Corp., have deep, suspicious ties with China's government.

"We can only surmise that the step-up in blocking is linked to the increase in rhetoric and threats of retaliation sparked by the (FBI) 'wanted' posters with (People's Liberation Army) officers, plus the smoldering resentment from the (Edward) Snowden disclosures," said Duncan Clark, chairman of BDA, a Beijing investment consultant firm.

"All of this is emboldening the nationalist and protectionist camp, and weakening the voices of more pragmatic actors" such as corporate customers, consumers and those concerned about trade frictions, he added.

China - which has more than 600 million Internet users - accounts for a minuscule part of Google's business operations. The company's profile and market share on the mainland have diminished since 2010, when the company said it would not abide by Beijing's censorship rules and began redirecting mainland users to its Hong Kong site, which does not face the same restrictions. The company does maintain some operations in China, however, and sells ads to mainland firms that want to reach Google users.

Today, 97 percent of Internet traffic in mainland China goes to in-country sites, but 3 percent goes to foreign sites and Google remains the most-visited non-Chinese property, according to GreatFire.org. Other popular U.S. websites including Facebook and Twitter are blocked in China.

Asked how barriers erected by the Chinese government have stifled Google's growth there, Colin W. Gillis, research director at BGC Financial, noted that Chinese search-engine company Baidu has built a market value of $62.4 billion in less than a decade. That's 17 percent of Google's total market value.

China's unfriendliness, however, may already be built into the company's stock price, he said: "The market has absorbed this fact since fall 2009 to early 2010."

Google's services are particularly popular with well-educated urbanites and academics in mainland China, who use Google products for teaching and research.

Zhan Jiang, a journalism professor at Beijing Foreign Studies University, said the Google blockade makes it difficult for him to download materials for his classes.

"Even people who generally support the government see this as a closing of borders," he said. "A lot of people are discussing this and are worried about this. ... It does seem to be an indicator of China-U.S. relations, and maybe if things warm up, the block will be dropped."

The extensive disruption of Google services comes as mainland authorities have been cracking down on in-country tech companies as well, going after sites and services with suspected ties to pornography, fraud, terrorism and violence. Just last week, for example, Chinese Internet behemoth Tencent said it had closed 20 million accounts on its WeChat messaging app that allegedly were linked to prostitution.

Amid a recent spate of terrorist incidents in western China and elsewhere, government officials have said repeatedly that separatists are drawing inspiration from foreign websites - in some cases by using a VPN, or virtual private network, which allows users to scale China's "Great Firewall" and access overseas sites unfettered.

Yi and Zhan use VPNs too - for their academic and design work. Yi worries that authorities might begin trying to stifle use of such technology.

If Chinese tech companies could provide as good a service as Google, he said, he wouldn't object to authorities censoring the Internet. "I can understand the government's perspective - China has a complicated national situation and stability is very important," he said.

Steve Lin, a 30-year-old who works for a cross-border e-commerce company in Beijing, says the first thing he does in the morning is turn on his VPN on his computer. But the technology works less well on his mobile phone, making it hard to use Gmail or search on the go. He also found he's been unable to use his Google Chromecast, a thumb-size, $35 device that plugs into a TV and allows users to send online videos, music, photos and other content to their television sets.

"I just got it last week and couldn't install it," he said. "It's totally annoying; it doesn't work at all in China."

GreatFire.org recently launched a new service that allows mainland Internet users to access Google search without a VPN. The so-called mirror site, available at SinaApp.co, is integrated with Amazon's cloud computing services, and the creators believe there is no way for China's Internet censors to block the site without also shutting off access to vast numbers of other pages - including many that belong to top companies - that also rely on Amazon's cloud.

Word of the mirror site has been spreading in China.

"Google could do this themselves, and very quickly, and much better than we can do it. I'm not sure why they're not" doing it, said the GreatFire.org founder.

"We're doing it because we believe Chinese should have free access to information. They shouldn't be treated as second-class citizens."

Explore further China blocks Google sites ahead of Tiananmen anniversary: group

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