NAJAF, Iraq - Gunmen opened fire on a U.S. Army vehicle today in Najaf's twin city, wounding two American soldiers and raising fears over the agreement struck the day before to end the bloody standoff around this Shiite holy city. Mortars fell on the main U.S. garrison but caused no injuries.

Armed members of Muqtada al-Sadr's militia - some of them masked and brandishing rocket-propelled grenade launchers and Kalashnikov rifles - roamed the streets of Kufa today. Most of the shops were closed and the streets were largely deserted. Three people were killed and eight injured in armed clashes, hospital workers said.

Elsewhere, U.S. troops escorting a convoy of inmates released from the Abu Ghraib prison briefly exchanged fire with assailants. It was the third major release from the facility since the scandal broke over the abuse of detainees last month.

On Thursday, Shiite leaders announced a deal with radical Shiite leader Muqtada al-Sadr to halt the fighting between U.S. troops and his radical militia, the al-Mahdi Army. The U.S.-led coalition said it was not a party to the agreement but would suspend offensive operations.

Despite the agreement, nine mortar shells hit the main U.S. camp in the Najaf area on this morning, according to CNN, which has a correspondent embedded there. U.S. soldiers detained four suspected militia members who said they were unaware of the truce, CNN said.

The U.S. command in Baghdad said gunmen fired on a U.S. Humvee on a street in Kufa, which adjoins Najaf. The command confirmed two Americans were wounded but provided no further details.

Later today, explosions were heard in the Kufa area but it was unclear what caused them. U.S. forces blocked the highways leading to the city. Gunmen from al-Sadr's militia could be seen in Kufa's streets.

During the seven-week standoff with the coalition, al-Sadr had appeared every Friday in a mosque in Kufa to deliver the traditional sermon. He did not show up today, however, and it was unclear why.

An al-Mahdi fighter told an Associated Press reporter that U.S. armored vehicles approached the mosque early today and the militiamen opened fire. He said three militiamen were killed but it was unclear if they were the same casualties reported by the hospital.

The truce deal announced Thursday provides the Americans a way out of a standoff that threatened to alienate Iraq's Shiites - the largest religious community. But U.S. demands for al-Sadr's arrest and disbanding his militia were unmet - and the deal opens the door for a political role for a figure that President Bush had branded a "thug."

The deal also allows for discussions of al-Sadr's future, talks that will certainly stretch past the June 30 handover. The arrest warrant for al-Sadr, however, has not officially been suspended.

Gunmen ambushed a convoy carrying Salama al-Khafaji, a member of the Iraqi Governing Council, as she was returning Thursday to Baghdad from mediation efforts in Najaf. She was not hurt but at least one bodyguard and her 18-year-old son were killed. The son was first reported as missing but his body was found today, according to her aides.

The ambush occurred 10 days after the head of the Governing Council, Izzadine Saleem, was assassinated in a suicide car-bombing as he waited to enter the heavily guarded Green Zone, the Baghdad headquarters of the U.S.-run occupation authority.

A group believed led by al-Qaida-linked terrorist Abu Musab al-Zarqawi claimed responsibility in a message posted on an Islamist Web site. However, al-Khafaji told The Associated Press she believed her attackers were Saddam Hussein loyalists who have attacked vehicles in that area before.

Al-Khafaji is one of three women on the Governing Council. She replaced another Shiite woman member, Aquila al-Hashemi, who was mortally wounded in September during an ambush near her Baghdad home.

She said it was clear the attack was targeted at her. "They looked at us and knew who we were," she said. "They went away to get their weapons and came back. The attack lasted a few minutes and my driver's priority was to speed ahead and leave the scene of the attack," she said.

The exchange of fire at Abu Ghraib took place after U.S. forces in Bradley fighting vehicles halted the convoy of buses with the freed detainees. Hundreds of relatives parked their cars, blocking traffic in both directions, and rushed the buses to find their loved ones.

Many relatives ignored warnings from the U.S. troops who pointed their rifles and yelled at them to stay back.

In previous releases, detainees were escorted all the way to their hometowns. Today, detainees headed for Baghdad got out of the bus and left in the hundreds of cars that had raced after the buses out of the prison gates.

Most of the buses continued on to destinations including Tikrit, Baquoba and Kirkuk. There was no immediate figure for the number of prisoners released, but the U.S. military said they would set up to 600 people free, reducing the number of those still detained to under 3,000.

The U.S. soldiers fired bursts of gunfire after shots were fired, apparently at the convoy. A reporter at the scene didn't see casualties.

Several tanks arrived and monitored the area for another hour, but there was no more fighting.

The release came about a week after the first American accused in the scandal was sentenced to a year in prison for sexually humiliating detainees and taking a photo of prisoners stacked naked in a human pyramid.

Also today, Iraqi gunmen released three veteran NBC News journalists and an Iraqi freelancer, three days after the group was captured in Fallujah, NBC said in a statement.

The statement said local Iraqi leaders helped mediate with "armed Iraqis," who let the reporters go "after their identities as working journalists became clear."

NBC identified the four as correspondent Ned Colt, cameraman Maurice Roper, sound technician Robert Colvill and freelance Iraqi journalist Ashraf Al Taie. It said they appeared to be in good health.

The group's Tuesday capture was never announced for security reasons, NBC said.

Gunmen attacked a car carrying two Japanese journalists late Thursday, and the car burst into flames. Today, a Japanese government spokesman said two bodies found near the site of the attack were identified as Japanese citizens.

The bodies have not been fully identified as the missing freelance journalists, Shinsuke Hashida, 61, and his nephew, Kotaro Ogawa, 33, but hospital workers told Japanese Embassy officials that the dead were Japanese, said Yu Kameoka, a spokesman for Prime Minister Junichiro Koizumi.

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Associated Press correspondent Anthony Deustch contributed to this report from Abu Ghraib.