Defying a ban on dissent, dozens of anguished mothers and angry young men held a rare unsanctioned protest today, taking to the streets of Baghdad to demand that President Saddam Hussein's government provide information about relatives jailed for political crimes.

The brief but boisterous demonstration, which occurred in front of the Information Ministry building, where foreign journalists have offices, shocked political observers here and left them wondering about its meaning. "Something like this has never happened before," said Wamid Nadhmi, a political science professor at Baghdad University. "It's a very, very important and unusual event."

The protesters, almost all Shiite Muslims, were upset that their relatives had not returned home after Hussein granted an amnesty to almost all the country's prisoners on Sunday. The unprecedented mass pardon sparked bedlam as prisoners overpowered their guards and stormed out of their cells while anxious relatives clambered over penitentiary walls.

In brief interviews before police dispersed the demonstrators and Information Ministry officials ordered journalists away from the crowd, several participants said their relatives had been arrested on charges of participating in political opposition movements, which are illegal in Iraq.

Diplomats, political analysts and even ordinary Iraqis who witnessed the spectacle were unsure of its significance. Some suggested it indicated that opposition to Hussein's more than two decades of rule might be growing. Others, however, cast the event as an epilogue to Sunday's amnesty, perhaps indicating that the release of thousands of prisoners, seen by many as an astonishing act of benevolence by Hussein, may have led people to believe their iron-fisted president had mellowed and now would tolerate public complaints.

One diplomat here said the protest was an indication that Hussein's government, facing the prospect of another war with the United States, was in the early stages of "losing control." But another diplomat said it was too early to draw conclusions about the protest, which was confined to a small part of downtown Baghdad and received no immediate coverage on state-run television and radio stations.

"At this point, it appears to be an isolated event," he said. "It's not something that proves that the Shiites are rebelling again. As far as we know, Saddam is still firmly in control."

Hussein's government, which is dominated by Sunni Muslims, has long been concerned about dissent among Shiites, who account for more than 55 percent of the country's 23 million inhabitants but have comparatively little political influence. Thousands of Shiites participated in a revolt against Hussein in southern Iraq in 1991, after the Persian Gulf War.

The protesters held two demonstrations today. The first one, around noon, attracted about 200 people and was preceded by a banner-waving march down a busy downtown street. Rather than criticize Hussein, the protesters extolled him. A few held aloft glossy posters of the president. A large white banner, originally created for last week's presidential referendum, read: "Yes, yes, yes to Saddam."

But in between the clapping and the cheering, several participants told foreign journalists that their real reason for showing up at the Information Ministry was to ask for information about their relatives from Information Minister Mohammed Saeed Sahhaf, who read Hussein's amnesty declaration on television Sunday.

"Where is my son?" wailed one woman. "Where was he taken?"

Several participants tried to force their way into the building, first through a door leading to the offices of foreign news organizations and then through a back entrance. Security officials pushed them back and asked them to disperse, but the crowd refused to leave the parking lot.

Finally, after about 30 minutes, a ministry official promised to convey their complaints to Sahhaf. A few moments later, a green-uniformed policeman fired an AK-47 assault rifle into the air and ordered the protesters to move away from the building, delivering a clear message that public dissent still is verboten here.

Draped in a black veil that exposed only her weathered face, Fathea Abdullah Ali, 52, said she was trying to locate her 30-year-old son, Hadi Ali Daoud, who was imprisoned two years ago. She said she had not seen her son since his arrest. Before reporters could ask her any more questions, though, a security official pushed her back into the crowd.

The failure of the protesters' relatives to return suggested that they died in prison or that Hussein's government is still holding people it deems politically sensitive. Government officials had said every prisoner would be freed except those charged with spying for the United States or Israel.

Human rights groups have accused the Iraqi government of summarily executing many prisoners, including scores of Shiite political dissidents.

A small group returned to the Information Ministry about two hours later. They, too, chanted slogans of support for Hussein before once again beseeching ministry officials for information about their relatives. After more journalists showed up to cover the demonstration, security personnel forced the group to keep walking down the street before finally ordering them to disperse.

Two women who remained at a street corner a block away said they were trying to locate their sons; one was arrested two years ago and the other was picked up in 1991.

"I don't know where he is," cried the woman whose son was jailed two years ago. "I don't know if he is living or he is dead. I don't know. I don't know."

The other woman said, "We've looked around, but found nothing."

Moments later, a red sedan pulled up at the corner. The driver, apparently an acquaintance of the women, shouted, "Get in! Get in!"

Because of the police presence, it was difficult for journalists to ascertain where else the group had demonstrated and how the relatives had organized. Some participants said they were from Baghdad, while others said they hailed from Shiite-dominated cities in southern Iraq.

Nadhmi said he doubted such a group could have jelled spontaneously, particularly given the venue. "To have a demonstration means there must be some sort of organization behind it," he said.

But Nadhmi, like the diplomats and others interviewed here, said he had no idea who might have been behind the protest. "It's a mystery," he said.

Demonstrators outside Iraqi Information Ministry demand details about political prisoners. Protesters, mostly Shiite Muslims, defy a ban on dissent as they march on the Iraqi Information Ministry.