BAGHDAD, Iraq – Hostage American reporter Jill Carroll appeared in a silent 20-second video aired yesterday by Al-Jazeera television, which said her abductors gave America 72 hours to free female prisoners in Iraq or she would be killed.

The tape showed the 28-year-old reporter sitting in front of a white background and speaking, but her voice could not be heard. On the tape, Ms. Carroll is pale and appears tired, and her long straight, brown hair is parted in the middle and pulled back from her face.

Al-Jazeera would not tell the Associated Press how it received the tape, but the station issued its own statement calling for Ms. Carroll’s release. An Al-Jazeera producer said no militant group’s name was attached to the message that was sent to the station with the silent tape yesterday.

However, a still photograph of Ms.Carroll from the videotape that later appeared on the Al-Jazeera Web site carried a logo in the bottom right corner that read “The Revenge Brigade.” The group was not known from previous claims of responsibility of violence in Iraq.

Ms. Carroll is a freelance reporter for the Christian Science Monitor, and the newspaper released a statement from her family pleading with her captors to set her free.

“Jill is an innocent journalist and we respectfully ask that you please show her mercy and allow her to return home to her mother, sister, and family,” the statement said. “Jill is a friend and sister to many Iraqis and has been dedicated to bringing the truth of the Iraq war to the world. We appeal for the speedy and safe return of our beloved daughter and sister.”

The State Department responded to the videotape with a statement that American officials were doing everything possible to win Ms. Carroll’s freedom.

“We continue to make every effort we can, working with Iraqis and others, to see Miss Carroll is returned safe and sound,” a spokesman, Sean McCormack, said.

Ms. Carroll was kidnapped January 7 in one of Baghdad’s most dangerous neighborhoods. Gunmen ambushed her car and killed her translator shortly after she left the offices of a Sunni Arab politician, who failed to show up for the interview.

The American military raided a prominent Sunni mosque a day after Ms. Carroll was kidnapped, sparking a demonstration by hundreds of worshippers. An American military official said the raid was a necessary immediate response to the kidnapping based on a tip provided by an Iraqi citizen.

Ms. Carroll, who speaks some Arabic and wore a head covering while moving around Iraq, has been described by her editor as an aggressive reporter but not a reckless one. Insurgents in Iraq have kidnapped more than 240 foreigners and killed at least 39 of them.

Her abduction occurred as Sunni Arab politicians are discussing their possible participation in a coalition government, which America hopes will help defuse the Sunni-led insurgency and heal sectarian rifts between Sunnis and Shiites.

President Talabani predicted yesterday that the country’s most prominent Sunni Arab political group would join a national unity government once December 15 election results are announced. No date has been set for the results’ release.

Also yesterday, a court official said a Shiite lawyer is expected to take charge of Saddam Hussein’s trial in the 1982 massacre of more than 140 Shiites, replacing the Kurdish chief judge who resigned amid claims of government interference in the high-profile case.

The second-ranking member of the five-judge tribunal trying the former Iraqi leader and seven co-defendants, Said al-Hamash, is expected to replace chief judge Rizgar Mohammed Amin, the top investigating judge who prepared the case against Saddam, Raid Juhi, said.

Judge Amin’s expected resignation followed complaints over the slow progress of the trial into allegations of Saddam’s involvement in the 1982 Dujail killings north of Baghdad following an assassination attempt against him.

The switch is not expected to prevent the trial’s January 24 scheduled resumption. The trial recessed December 22 after two days of testimony. Conviction could bring a sentence of death by hanging.

Judge Amin would be the second judge to step down. Another panel member removed himself in late November because one of the co-defendants may have been involved in the execution of his brother.

Since the trial opened October 19, two defense lawyers also have been assassinated and a third has fled the country. Police also uncovered a plot to fire rockets at the courtroom in late November.

Mr. Talabani would not object to moving the tribunal from Baghdad to southern Iraq or his northern Kurdish region if the judges sought such a change on security grounds, presidential secretary Hewah Othman told the Associated Press. But any transfer is dependent on parliamentary approval.

Elsewhere, gunmen firing from cars terrorized the western Baghdad neighborhood of al-Baiyaa yesterday, slaying a police lieutenant driving to work before three more men – including an auto mechanic and his son – were gunned down in the same area.

Earlier in the day, the bullet-riddled bodies of an army battalion commander and his brother were also found in al-Baiyaa. Colonel Hussein Shiaa and his brother were abducted Sunday after leaving their base in Mahmoudiya, about 20 miles south of Baghdad.

Police found four bound and blindfolded bodies each shot in the back of the head and dumped in a Baghdad sewer, police said.