Police battled demonstrators in downtown streets and one man was shot to death tonight following a "March for Democracy" that drew tens of thousands to the presidential palace to shout their contempt of the ruling armed forces.

The anti-government demonstration was described as the largest in the more than six years of military rule. Authorities reported that approximately 35 policemen were injured in street fighting along with an estimated 30 protesters, and at least 120 persons were arrested.

The crowd, estimated at more than 100,000 persons by observers and independent Argentine news services, gathered in columns organized by major political parties, labor unions and human-rights groups this evening before marching down the wide diagonal avenues leading to the central Plaza de Mayo.

Once in the plaza, the protesters turned to the pink stone presidential palace, seat of the military government, and roared approval as political leaders denounced the military and demanded general elections for a civilian government in six months.

As the crowd in the plaza swelled, a few protesters tossed rocks at police and nearby buildings, and police responded by firing tear-gas canisters into the packed plaza.

Most of the peaceful demonstrators streamed away from the plaza, pursued by tear gas, while groups of protesters remained to battle police.

Fleeing militants built trash fires in nearby streets, and many moved in crowds through downtown, hurling rocks, paving stones and firecrackers at police mounted on horses or in armored cars.

Police fired back tear gas and blank charges. Sirens wailed, window glass shattered and tear-gas canisters continued to explode in downtown Buenos Aires for more than an hour after the end of the massive demonstration.

Authorities reported tonight that one young man died after he was hit by gunfire near the Plaza de Mayo.

Argentine news services quoted witnesses as saying that the shots came from a passing Ford Falcon sedan, a type of automobile that long has been identified here with paramilitary forces.

The march, unsuccessfully discouraged by the government, was organized by Argentina's five largest political parties.

The parties last month had summarily rejected a government proposal to negotiate a national covenant governing Argentina's return to democracy.

It was the culminating event in a two-week series of nearly daily protests, marches and strikes in opposition to military rule, human-rights abuses and current economic policies. Since Argentina's humiliating loss of the Falkland Islands war with Britain last June, the military's rule has grown progressively weaker and there have been fears of a governmental collapse or a new hard-line coup to stifle the growing public unrest.

Political leaders and analysts here expected the military government to carefully gauge the outcome of today's rally before deciding how to proceed on its current plan for a covenant that would give the armed forces substantial control over a civilian government elected late next year.

In an effort to prevent an outbreak of violence that was feared would provoke an extreme military reaction, opposition leaders today organized their own security force of approximately 1,500 irregulars who lined the march routes with linked arms and broke up shoving matches between competing factions.

According to witnesses, it was a small number of protesters who appeared to provoke the massive discharge of tear gas into the crowd.

As the demonstration had gathered strength in the Plaza de Mayo, the diverse crowd of students, factory workers and middle-class citizens stood beneath a hot setting summer sun and tirelessly chanted such antimilitary slogans as "It's going to end, the military dictatorship," and "Up against the wall, all the brass who sold the country."

There were also loud chants of "the disappeared--tell us where they are," and some groups carried banners with pictures of leaders alleged to have been abducted and killed by government paramilitary forces.

The rhetoric of the demonstration's leaders was also strong.

The Multi-Party Movement, a grouping of the country's five largest political parties, delivered a statement to a government representative harshly criticizing the military's relatively conservative economic management and demanding the implementation of a populist program drawn up by the party leaders.

The document asked for general elections by next May, and for a transition to a new democratic government next October.

It also called on the military to provide a public account of its actions in the Falklands conflict and the violent campaign against terrorists and internal opponents that left an estimated 6,000 to 15,000 missing in the late 1970s.