Militants linked to wanted terrorist Abu Musab al-Zarqawi say they have killed a second American hostage in Iraq.
An Internet message announced the killing of the hostage (Jack Hensley) and threatened the execution of a Briton (Kenneth Bigley) abducted last week with the two Americans.
On Monday, a video was released showing the beheading of the other American hostage (Eugene Armstrong).
The militants demanded the release of women prisoners they said were held by coalition forces in Iraq. Britain denies holding any female prisoners. U.S. officials say they are holding two female scientists accused of working on Saddam Hussein's weapons program.
Meanwhile, U.S. forces pushed into Baghdad's Sadr City neighborhood in an effort to flush out insurgents based there. Loud explosions rocked the area as the operation began early Wednesday.
Information for this report is provided by Reuters, AFP and AP.