The US non-profit Public Broadcasting Service (PBS) denounced hacker strikes on its news websites as "chilling and irresponsible" attacks on journalism.
PBS was targeted by hackers in retaliation for an in-depth look at whistle blower website WikiLeaks in a "Frontline: Wiki Secrets" film broadcast last week, according to spokeswoman Anne Bentley.
Cyber attackers marred PBS web pages with graffiti, exposed account information of member stations, and posted a fake story about late rap musician Tupac Shakur being alive in New Zealand.
The "intrusion to PBS servers" began late Sunday and continued into Monday morning, according to Frontline.
"We see it as a disappointing and irresponsible act," said Frontline executive producer David Fanning.
"We have been very open to publishing criticism of the film, and the film itself included multiple points of view," he continued. "Rather than engaging in that spirit, this is an attempt to chill independent journalism."
PBS was hit with more cyber attacks on Monday, according to Bentley.
"The intruders also posted login information to an outdated version of PBS PressRoom and an internal communications website for stations," Bentley said Tuesday in an email response to an AFP inquiry.
"We have notified stations and affected parties to advise them of the situation."
PBS had restored its websites.
The WikiSecrets film and a forum of comments it has drawn were online at pbs.org/wgbh/pages/frontline/wikileaks/.