Al-Jazeera said that in a message accompanying the 20-second video, the kidnappers said they would kill Carroll within 72 hours if the United States does not release female prisoners in Iraq. The television station did not say how it obtained the video.
A previously unknown group calling itself the Brigades of Vengeance has apparently claimed responsibility for the abduction.
The U.S. State Department said the U.S. government was making every effort to get Carroll released as soon as possible.
The journalist's family has appealed to the kidnappers to show mercy and release the 28-year-old, saying she is innocent.
(compiled from agency reports)