Google has accused China of blocking Gmail after weeks of disruptions to the firm's e-mail service to users in the country.
Google said there are no technical issues with the service, according to news reports.
"This is a government blockage carefully designed to look like the problem is with Gmail," the company said in a statement.
Google confirmed that the application it created to help people locate friends and relatives missing in Japan after the earthquake and tsunami has also been affected by the blockage, other reports said.
Several reports have linked the disturbances to online calls for so-called "Jasmine rallies" in China, inspired by uprisings in the Middle East and North Africa.
Web experts report that internet controls have been increased because the Chinese government thinks activism on the Internet is a threat.
Google's complaints come just a year after the company reported that it had been targeted by cyber attacks aimed at accessing the Gmail accounts of Chinese human rights activists.
The attacks on Google and around 30 other US-based companies were widely considered to be evidence of pervasive and sophisticated cyber espionage being carried out from China, but Chinese officials denied any state involvement.