In perhaps the boldest civilian challenge yet of Argentina's current military rulers, more than 7,000 people turned out for a march today that the government had banned.

Police stood by until the marchers neared the main plaza where the presidential palace is located. An exultant Adolfo Perez Esquivel, a Nobel Peace Prize winner and one of the march organizers, said: "Our goal of arriving at the Plaza de Mayo has not been realized. But, yes, we have arrived at the plaza of the nation's conscience."

The mostly peaceful downtown demonstration was the second mass protest against the rule of President Reynaldo Bignone in less than two weeks and was seen by observers here as a victory for those demanding a return to civilian rule.

The "March for Life" was held to protest continuing official silence about the fate of thousands of Argentines who "disappeared" during the military's campaign against leftists in the mid-1970s. From 6,000 to 15,000 are estimated to have been abducted and killed, most of them since the military took power in 1976.

The demonstrators were led most of the way by white-kerchiefed women of the mothers and grandmothers of the Plaza de Mayo--who for several years have gathered outside the palace to seek information on their children. "Where are the hundreds of babies born in captivity?" asked a placard.

As the police continually fell back from the marchers, chants of "Liberty, Liberty, Liberty," mixed with choruses of "To the firing squad." Hundreds of police in full riot gear prevented the demonstrators from nearing the palace, clubbing those who tried to break through. Official reports of arrests and injuries were not available.

The protest was by far the largest devoted strictly to the issue of human rights. A march called by the militant wing of the Peronist labor confederation late last month drew about 25,000 people demanding economic changes.

An Interior Ministry communique announcing the ban on the march had said it "in no way contradicts the gradual political opening and the recognition of the right of assembly and freedom of expression," but the march would not "promote the public good, because it aims at deepening the wounds caused by the terrorist war."

Emilio Mignone, president of the Center for Legal and Social Studies, a march organizer and a parent of a "disappeared" daughter, said the Interior Ministry statement was "absurd. Either there is freedom or there isn't."

A number of leaders representing a wide range of the civilian spectrum helped lead the rally -- including former vice president Vincente Solano Lima, and Roman Catholic Archbishops Jorge Novak and Jaime de Nevarez.