Several Google websites have been blocked in China ahead of the 25th anniversary of the Tiananmen Square crackdown, a censorship monitoring service said.
China prevents access to a host of websites including YouTube and Twitter using a system known as the "Great Firewall," and restrictions are tightened ahead of dates the government considers sensitive.
Overseas versions of Google, accessible in China after the technology giant withdrew from the mainland in 2010, have now been blocked, according to GreatFire.org.
"The block is indiscriminate as all Google services in all countries, encrypted or not, are now blocked in China," it said on Monday.
Affected products include Gmail, images, and the search and translation service, alongside country specific versions of Google homepages.
The move comes ahead of the anniversary of the 1989 crackdown on pro-democracy protests in Beijing, which killed hundreds, by some estimates more than 1,000.
China's ruling Communist Party tightly controls public discussion of the June 4 crackdown.
"Because the block has lasted for 4 days, it's more likely that Google will be severely disrupted and barely usable from now on," the website said in a statement on Monday.
"The 25th anniversary of the Tiananmen Square incident is coming. This highlights another fierce battle in the war between China censorship authority and information flow," it added.
Google stopped offering a search engine service within mainland China in 2010, citing censorship, but users were redirected to the Hong Kong version which was usually accessible, although sometimes blocked.
Google said the shutdown was not on its side.
"We've checked extensively and there's nothing wrong on our end," a Google spokesman told AFP, adding that Google services are partially accessible in China.
China's government generally responds to queries about blocked websites by saying it that it manages the Internet according to the law.
Google's share of China's online search market stood at just 1.2 percent in April, according to Chinese market research company CNZZ.