Mass demonstrations on a national day of protest yesterday appear to have revitalized opposition to the government of Gen. Augusto Pinochet and frustrated government efforts to end its political crisis with a careful mixture of repression and conciliation.

Protest organizers and progovernment Chilean newspapers concurred today that a strict curfew and the deployment of military forces had failed to stop an impressive showing in Santiago last night by citizens who banged empty pots and pans from their windows and balconies.

Although street demonstrations had been discouraged by opposition leaders, hundreds of other persons defied the 8 p.m.-to-midnight curfew and built barricades in working-class neighborhoods. During the day, protesters occupied the central court building and students demonstrated and battled police on half a dozen campuses.

Police reported this morning that one person had been killed and another wounded by gunfire and 560 arrested in Santiago during the night. A second death was reported in the port city of Valparaiso, and there were numerous reports of bombings. Witnesses said shots had been fired by unidentified persons in unmarked cars.

Newspaper and police reports contradicted assertions by government officials that "absolute tranquility" had prevailed yesterday and appeared to deal a blow to the prestige of Pinochet and other high-ranking military leaders, who had vowed publicly that no more protests would take place.

At the same time, the protest preserved an opposition movement that is seeking to mobilize public support for a quick return to democracy. Pinochet, who took power following a 1973 military coup against Socialist president Salvador Allende, is scheduled to rule until at least 1989.

Drawing on widespread dissatisfaction with a two-year-old recession and continuing political repression, the loose alliance of union leaders and political parties also organized large antigovernment demonstrations in May and June.

Those successes were followed, however, by a precipitate move toward a general strike and a strong government crackdown that left the opposition divided, deprived of much of its leadership and apparently close to collapse.

The new protest, organized largely by the officially outlawed but still powerful Christian Democratic Party, appeared likely to add strength to party factions seeking to organize a broad front to oppose Pinochet and demand his resignation within the coming weeks. Additional national protests already have been planned by the party for early August and September, the 10th anniversary of the military coup.

However, opposition leaders concede that their movement is still relatively weak compared with the one that prepared the way for the coup against Allende with massive strikes and demonstrations.

Despite the apparent willingness of many middle and working-class Chileans to join large antigovernment protests, opposition leaders still lack the support of key middle-class groups representing businessmen and conservative politicans, these leaders say.

The government strategy of combining repression with moves toward a political opening, along with serious tactical mistakes by the opposition, have badly damaged the protest organization, party leaders say. Moreover, the opposition alliance, even the various factions within the Christian Democratic Party, has been unable to agree on a platform or a plan of government that could be proposed to the armed forces.

"We are not going to succeed quickly," said Gabriel Valdes, the president of the Christian Democrats, in a recent interview. "This is a long-term operation that will have to go through its up and down cycles. We have to create a scenario that will convince people that after Pinochet there will not be chaos."

Valdes, a former foreign minister, was jailed Saturday by a judge along with two other party leaders for suspected involvement in the distribution of leaflets calling for yesterday's protests. Tonight, however, Valdes and the other two men were released unconditionally by a judge's order.

While the jailing of Valdes appears to have helped the opposition movement by antagonizing moderate and conservative politicans and drawing vigorous diplomatic protests, Pinochet has moved effectively in recent weeks to neutralize or dismantle much of the array of unions, parties and business associations opposing him.

The last two national protests were formally called by an alliance of labor unions led by Rodolfo Seguel, a 29-year-old copper worker whom Chileans compare to Poland's Lech Walesa. Seguel has now spent a month in jail on criminal charges, however, and his once powerful Confederation of Copper Workers has been crippled by the firing of 31 union leaders and 799 workers following a two-day strike last month.

Government officials have skillfully manipulated labor leaders to break them off from the protest movement. When copper union leaders, under pressure from the rank and file, met with officials last week to ask that workers be rehired, they were told a response would be delivered today, one day after the national protest.

The copper workers did not participate in organization of the new demonstrations, and the government subsequently neutralized the participation of other key middle-class sectors. Most significantly, the National Truckers Association, which threatened to spearhead a movement of conservative businessmen and farmers against the government after a failed national strike last month, moved away from open confrontation after the government agreed that $120 million in truckers' debts would be refinanced.

These developments had left Chilean political leaders relatively isolated in seeking direct confrontation with the military government and the removal of Pinochet. Party leaders, who include Christian Democrats, Socialists, centrists, Radicals and some disaffected conservatives from the National Party, said their most important task now is to prepare a platform of opposition that would draw in the business associations and more of the political right.

The Christian Democrats and their allies in a loose organization called the Democratic Manifesto are plagued by poor organization and internal disputes, however. Despite months of effort, the Christian Democrats still have not agreed on a draft of a platform that could be presented to the other parties for approval.

Many of the obstacles to an opposition consensus are related to the fractious politics of Chile's past. One of the key issues that continues to divide the Christian Democrats from sectors of the right as well as some Socialists, for example, is debate over the role in the opposition front and future legal status of the Communist Party, which won 16 percent of the vote in Chile's last election before the 1973 coup.

Party leaders also are under heavy pressure from more militant, mostly younger politicians demanding that more action be taken. Fifty-four party activists under 40 have already formed their own organization and issued a public declaration calling for Pinochet's resignation and the scheduling of elections in six months.

With the opposition lacking a clear program or organization, many political leaders have become concerned that Pinochet could defuse the political crisis by initiating a political liberalization that would preserve his tenure as president.

In fact, this alternative is being urged on Pinochet by conservative supporters inside and outside the government. Government moderates and an influential right-wing movement of supporters have urged Pinochet to appoint a new prime minister with broad powers to initiate such an opening. Under the present government structure there is no prime minister.

In recent weeks, union leaders, businessmen, and moderate politicians in the opposition have been approached by a former Air Force general, Nicanor Diaz Estrada, who outlined the plan and said it was supported by high-ranking military leaders, according to several sources.

Political leaders close to the government say, however, that advocates of the political opening under a prime minister have been unable to persuade Pinochet to accept their plans, which would diminish the 67-year-old leader's personal power.