BEIJING - Experts have warned that the inaccessibility of many Chinese websites on Tuesday posed information safety risks and could have been exploited by hackers.

For a period around 3 pm on Tuesday, attempts to visit many Chinese websites failed, with netizens often receiving error messages. This was due to malfunction of root servers for China's top-level domain names, the China Internet Network Information Center (CNNIC) said in a posting on Sina Weibo, the Twitter-like microblogging service.

The accessibility of the websites has returned to normal, the CNNIC said.

360 Safe Guard, a popular Internet security software brand by Qihoo 360 Technology Co., said in a Weibo posting that visits to many sites were redirected to 65.49.2.178, a U.S.-based IP address.

Song Yingqiao, an expert with www.net.cn, a domain service provider, said such failures could be exploited by hackers, with the IP address being used to phish for users' information, for example. However, the address did not respond to the visits, so there have not been reports of any personal information leaks, Song said.

Dong Fang, an expert with Qihoo 360, agreed, saying that the possibility of the problem being the result of a hacker attack cannot be ruled out at present."Theoretically, if hackers take control of the root servers, they can make phishing websites to lure Internet users," Dong said.

He added that it is difficult to take precautions against this kind of incident, but that affected companies should make timely responses and provide remedy plans.