The U.S. State Department says it has launched an online effort to counter al-Qaida propaganda placed on Yemeni tribal websites by replacing al-Qaida advertisements with ads aimed at undermining their message.

Secretary of State Hillary Clinton says U.S. digital experts are replacing al-Qaida ads that brag about killing Americans with ads showing the effects of al-Qaida attacks on the Yemeni people.

Clinton said at a dinner late Wednesday that the efforts are starting to have an impact on extremists who have been venting their frustration and asking their supporters not to believe everything they read online.

The al-Qaida ads appear on Yemeni tribal websites and are aimed at recruiting new members.

The effort is part of the State Department's new Center for Strategic Counterterrorism Communications, which aims to blunt al-Qaida propaganda placed on the Internet and social media.