All Google (GOOG) services, including its search engine, Gmail and Maps, were inaccessible in China on Friday night and into Saturday, the company confirmed. The block comes as the 18th Communist Party Congress, the once-in-a-decade meeting to appoint new government leadership, gets under way.
Traffic to Google sites fell off Friday evening in China, according to Google's Transparency Report, which provides information about traffic worldwide.
The company said it was not having any technical problems but did not say whether it believed its sites had been blocked by the government or were the victims of hacking.
"We've checked, and there's nothing wrong on our end," said Christine Chen, a Google spokeswoman.
Despite great fanfare, China's Party Congress takes place under wraps. Reporters are not allowed in, and in the days preceding the event, the government has imposed restrictions ranging from replacing books in bookstores to banning balloons because they could carry messages of protest.
Internet speeds have also slowed, while Chinese citizens have been satirizing the meeting online.
The block on Google sites appears to be the latest in a pattern of increasingly sophisticated Internet censorship by the Chinese government. It comes two weeks after China blocked Web access to The New York Times, following an article about its prime minister's family wealth.
Google has had a particularly strained relationship with China. In 2010, the company said it had been the victim of serious hacking attacks coming from China. In response, it removed its Chinese language search engine from China and began redirecting traffic to the Hong Kong version of the search engine.
YouTube, Google's video site, has been blocked in China since 2009. And Gmail has been partially blocked at various times, beginning around the time of the Arab Spring.