Now you see it, now you don’t.

A Chinese documentary that showed off the military’s ability to conduct a cyberattack against a U.S.-based site appears to have been removed from the Web site of state-run TV.

Meantime, Chinese officials are insisting that the clip was nothing but the workings of an imaginative producer.

The clip was part of a state-run documentary on cyberwarfare, and it appeared to show an unseen user conducting an attack on an Alabama-based Web site of the Falun Gong spiritual movement. At just six seconds, the clip offered what experts described as an uncommonly candid depiction of China’s offensive cyber-capabilities.

On Thursday, Internet users trying to find the documentary on the site of Chinese State Television would instead find the message “Error Page -- This page does not exist anymore.”

(The documentary can still be found on YouTube.)

China’s Defense Ministry said Thursday in an e-mail statement that the scene was the “pure action of the producer,” and that “the content and opinion of the program do not represent the policy and stance of the government.”

“China has always attached importance to Internet security, and firmly oppose to any form of Internet criminal activities,” the statement said. “Chinese military has never implemented any form of cyber attacks.”

China routinely denies responsibility for cyber attacks, as well as online espionage, despite widespread reports of such activity.

“The Chinese are relentless and don’t seem to care about getting caught,” Joel F. Brenner, then National Counterintelligence Executive, said in an April 2009 speech. “We have seen Chinese network operations inside certain of our electricity grids. Do I worry about those grids, and about air traffic control systems, water supply systems, and so on? You bet I do. Our networks are being mapped.”

The Pentagon’s annual report on China’s military, released on Wednesday, said that numerous computer systems around the world, including in the United States, were penetrated in 2010 in attacks that “appear to have originated” in China.

“Developing capabilities for cyberwarfare is consistent with authoritative PLA [People’s Liberation Army] military writings,” the report stated.

It noted that in a strategy journal, the Chinese write, “In the information war, the command and control system is the heart of information collection, control, and application on the battlefield. It is also the nerve center of the entire battlefield.”

While China State Television’s Web site no longer hosts the cyberwar documentary, the site did feature a story on Thursday about the new Pentagon report.

The Pentagon, the story said, “acknowledged China’s contribution to international security.”