Chinese authorities have blocked the search engines of two of the country's most popular web portals as part of their efforts to censor the Internet, industry sources, quoted by an AFP report, said.
The AFP report said the search engines at Sina.com and Sohu.com have been shut down since noon Monday.
Searches conducted brought up messages saying the sites were undergoing upgrades, the AFP report said.
China has for years been waging an online battle to censor the Internet of pornographic and violent content, and to seek to stifle political and religious material that it believes could spark social unrest, the report said.
'As of yesterday noon, all the databases have been in a state of closure because relevant government Internet supervision departments were censoring our databases,' the source, a member of customer service staff at Sina.com told AFP. 'It affects not just Sina, but Sohu as well, so our search engines are not in use.'
The AFP report further said another member of staff at Sina confirmed the government order, although the company spokeswoman's office declined to give a reason, saying the system was only going through an upgrade.
Sohu's spokesman was not available for comment but a content editor told AFP the company's database system had to be upgraded because of the large volume of visits.
Sina.com and Sohu.com are among 14 Beijing-based Internet portals which in April called on the industry to follow their example by self-censoring 'unhealthy' content from their Web sites.