The Chinese authorities are believed to have blocked a majority of domestic users from accessing Google.com. 

Press freedom group Reporters Without Borders claims that internet users in major Chinese cities have had difficulty accessing Google's international site for the past week.

The block is also said to be affecting Google News and Google Mail.

However, Google China, which blocks politically sensitive material to comply with government censorship rules, is not experiencing any such difficulties, according to Reporters Without Borders.

"It was only to be expected that Google.com would be gradually sidelined after the censored version was launched in January," said the organisation in a statement.

Cui Jin, a spokeswoman for Google in Beijing, insisted that the situation is being investigated.