The Web site of the Chinese Society for Human Rights, a state-run organization, was launched Monday, and contained links to government documents and other officially-sanctioned articles.
But visitors to the site saw a stark page of text with the headline "Boycott China."
"I simply can not believe the total b------- propaganda on this Web site," the crackers wrote, calling the Chinese government a "gang" of "thugs and bullies."
The page also contained links to Amnesty International and other human rights organizations who have been critical of the country's human rights record.
The incident is the latest to highlight the Web's use as a means of political action. The Mexican government site, for example, frequently comes under attack by crackers sympathetic to the cause of the Zapatista rebels in Chiapas.
The crackers of the China site, who identified themselves as Zyklon and Bronc Buster, also took the opportunity to give their views on the case of Kevin Mitnick, arrested in 1995 for computer crimes.
They boasted that breaking into the China site took only two minutes. "Your security is a total joke!" they wrote.