Correction: An earlier version of this article incorrectly reported that cyber experts had hacked into al-Qaeda’s sites to replace its rhetoric with information about Yemeni civilians killed in terrorist strikes. U.S. officials did post such information, mimicking the format used by the group, but they did so on publicly accessible forums. They did not gain unauthorized access to sites, and they did not alter content already on the sites. This version has been corrected.

State Department officials recently carried out a counter-propaganda campaign on Web sites being used by al-Qaeda’s affiliate in Yemen, challenging the group’s anti-American rhetoric with information about civilians killed in terrorist strikes, Secretary of State Hillary Rodham Clinton said Wednesday.

When al-Qaeda recruitment propaganda appeared on tribal sites in Yemen, Clinton said, “within 48 hours, our team plastered the same sites with altered versions . . . that showed the toll al-Qaeda attacks have taken on the Yemeni people.”

In a speech to the Special Operations Command in Tampa, Clinton cited the campaign as an example of growing counterterrorism cooperation among the State Department, the intelligence community and the military.

She said that State Department experts also are working with Special Operations Forces on the ground in Central Africa, helping to encourage defections in the Lord’s Resistance Army, led by Joseph Kony.

As the U.S. military has expanded its operations into areas formerly reserved for diplomats, Clinton has been an advocate for expanding her department’s reach, with civilian-military operations she calls “smart power.”

“We need Special Operations Forces who are as comfortable drinking tea with tribal leaders as raiding a terrorist compound,” she said. “We also need diplomats and development experts who are up to the job of being your partners.”

She added: “We can tell our efforts are starting to have an impact” in Yemen, where the group al-Qaeda in the Arabian Peninsula is based, “because extremists are publicly venting their frustration and asking supporters not to believe everything they read on the Internet.”

Clinton said the campaign was conducted by the Center for Strategic Counterterrorism Communications, based at the State Department, with expertise drawn from the military and the intelligence community.

The State Department’s activities are the latest in online counterterrorism efforts to stem the spread of radical Islamist ideology that stretch back at least a decade.

The U.S. Central Command has a digital engagement team that monitors blogs and forums, targeting those that are moderate in tone and engaging with users, said Maj. David Nevers, former chief of the team.

“We try to concentrate our energy and efforts . . . [on] those who haven’t been radicalized. The idea is to go where the conversation is taking place, using . . . extremist commentary or propaganda as a jumping-off point to people who are listening in,” Nevers said in an interview earlier this year.

Said Evan Kohlmann, an international terrorism consultant who tracks jihadist Web sites: “The fact is that al-Qaeda engages in tactics and ideologies that are by their nature exceptionally divisive and controversial. Highlighting that does a tremendous amount of damage to al-Qaeda’s image, to its recruitment campaigns and its effort to launch renewed attacks.”

But Kohlmann questioned the effectiveness of the tactic.

“Is publicizing this stuff on tribal forums reaching a wide enough audience to make a difference?” he said. “If you’re already living in Yemen and in a tribal area, you probably don’t need to go to a Web site to join al-Qaeda.”