Sporadic gunfire and explosions boomed through Najaf (search) on Thursday despite a peace deal in which radical cleric Muqtada al-Sadr (search) agreed to disarm his militiamen and pull them out of a revered Shiite shrine they've been taking refuge in.

As clashes in Najaf continued, Arab television station Al-Jazeera aired a video Thursday showing a militant group that called itself the Martyrs Brigade vowing to kill a missing Western journalist if U.S. forces do not leave the holy city within 48 hours. The authenticity of the tape could not be determined.

The deal announced Wednesday aimed to end two weeks of fighting between al-Sadr's forces and U.S. and Iraqi troops in this holy city.

Al-Sadr has made contradictory statements in the past, and aides to the cleric said he still wanted to negotiate details of the peace deal — including brokering a cease-fire prior to any disarmament.

In Washington, the Bush administration said al-Sadr needed to match words with deeds. "We have seen many, many times al-Sadr assume or say he is going to accept certain terms and then it turns out not to be the case," said National Security Adviser Condoleezza Rice (search).

The cease-fire agreement was announced at the National Conference in Baghdad, which had sent a delegation to negotiate with al-Sadr.

The conference, a gathering of more than 1,000 prominent Iraqis that was seen as an important milestone on the country's path to democracy, spilled into an unscheduled fourth day Wednesday so it could choose members of an interim National Council. The council is to act as a watchdog over the interim government until elections in January.

Disputes persisted at the conference throughout the day over how to choose 81 elected members of the council, with small parties complaining they were being strong-armed by the large factions into accepting their slate of candidates.

A planned vote to affirm a slate of 81 candidates was called off at the last minute, and the conference organizers simply affirmed the group — to the dismay of many of those who were not included in the council. The final 19 members of the 100-member council will be members of the former U.S.-appointed Iraqi Governing Council who were left out of the interim government.

The video aired by Al-Jazeera depicted a man, who resembled missing journalist Micah Garen, kneeling in front of five masked militants, who were armed with rifles and rocket-propelled grenade launchers.

The hostage, who had a mustache, looked down at the ground throughout the video. The sound was not audible, but the announcer said the kidnappers threatened to kill Garen within two days if U.S. forces did not leave Najaf. Garen's father and his fiancee were unavailable for comment.

According to witnesses, Garen and his Iraqi translator, Amir Doushi, were walking through a market in the southern city of Nasiriyah (search) on Friday when they were seized by two armed men, police said.

At the time of his abduction, Garen, 36, was working on a story about the looting of archaeological sites in Iraq, his fiance, Marie-Helene Carleton said.

Garen worked for New York-based Four Corners media, identified on its Web site as a "documentary organization working in still photography, video and print media." He has taken photographs as a stringer for The Associated Press and had a story published in The New York Times.

Neither U.S. nor Iraqi forces had any word on Garen's fate Wednesday.

In Najaf, al-Sadr's loyalists and a combined U.S.-Iraqi force have been fighting for nearly two weeks throughout Najaf, battling in the vast graveyard and in the streets of its Old City. A wall surrounding the Imam Ali Shrine, where the militants have holed up, was reportedly chipped in the fighting, and any damage to the gold-domed mosque itself would infuriate the world's 120 million Shiite Muslims.

The drawn-out fighting, which had spread to other Shiite areas, has already burnished al-Sadr's reputation among poor, grassroots Shiites at the expense of more senior — and more moderate — clerics and hampered the government's efforts to quell a separate Sunni insurgency.

Fresh gunfire and explosions were heard early Thursday despite the peace deal.

On Wednesday afternoon, Iraqi Defense Minister Hazem Shaalan said the government could send Iraqi forces to raid the shrine by the end of the day. Prime Minister Ayad Allawi issued a statement accusing the militants of mining the area around the shrine.

Hours later, al-Sadr's office sent a message to the conference, saying he would accept the gathering's peace proposal, which demands his militia drop its arms, withdraw from the shrine and transform itself into a political party in exchange for amnesty.

Sheik Hassan al-Athari, an official at al-Sadr's Baghdad office, said the cleric wanted to negotiate how the plan would be implemented and to ensure his militants would not be arrested. He said al-Sadr had other minor conditions, but did not elaborate.

Al-Sadr aide Ahmed al-Shaibany said U.S. forces must first stop attacking.

"They cannot ask us to disarm while ... they're using warplanes to fight us. There should be a cease-fire first and then they ask us to disarm," he said.

The U.S. military says the clashes have killed hundreds of militants, though the militants deny that. Eight U.S. soldiers and at least 40 Iraqi police have been killed as well.

At the Abu Ghraib prison, which was the center of a scandal over allegations that American prison guards abused Iraqi detainees, U.S. military police shot and killed two of the detainees and wounded five others during a massive brawl Wednesday, the military said.

Several detainees attacked an inmate with rocks and tent poles in a fight that soon encompassed 200 people, said Lt. Col. Barry Johnson, the U.S. military's spokesman for detention operations in Iraq. Abu Ghraib is west of Baghdad.

On Thursday, an Army spokesman said that attackers fired on a U.S. patrol in east Baghdad, killing one soldier. The American soldier died Wednesday in Baghdad's Sadr City neighborhood, scene of ongoing firefights between U.S. forces and al-Sadr's supporters, said Maj. Philip Smith.

The soldier was the second to die in Baghdad on Wednesday. The military had already announced the death of another American soldier who was shot dead while patrolling the same area hours earlier, Smith said.

In the central city of Hillah, two Polish troops were killed and five were injured early Thursday in a car crash that followed an ambush by insurgents, said Col. Zdzislaw Gnatowski, spokesman for the Polish army chief of staff.