One day after shuffling his Cabinet and promising a political liberalization, Gen. Augusto Pinochet faced renewed demonstrations against his authoritarian rule today, and at least four persons were killed in violent clashes between protesters and police and Army troops.

In a sharp intensification of four months of confrontation between the military government and its opposition, 18,000 police and soldiers occupied Santiago streets yesterday and today and were challenged by thousands of persons demanding Pinochet's resignation and return to democracy.

By late tonight, following a 6:30 p.m. curfew declared in the capital by the local military command, at least four persons were reported killed by gunfire from security forces. Earlier, at least seven persons were reported injured and more than 500 persons were unofficially reported arrested yesterday and today. A nationwide demonstration tonight by citizens banging pots and pans in their homes could be heard in Santiago for more than 1 1/2 hours.

Responding to the fourth consecutive monthly protest against military rule with the greatest force yet, military commanders stationed troops in full combat gear around Santiago beginning yesterday afternoon. Police quickly attacked with clubs, dogs and volleys of tear gas, and small tanks armed with water cannons circulated through the streets. Dozens of persons were reported to have been beaten by police.

With campuses occupied by police, students held demonstrations last night, built barricades and fought police with rocks. Confrontations were reported tonight in a number of working-class neighborhoods, and explosions and gunfire could be heard for hours after the curfew. Tracer bullets, fired by troops, could be seen around the city.

Extremist groups burned a dozen buses in attacks during the last three days, and there was little traffic in Santiago today. As the curfew approached on a sunny, late-winter afternoon, downtown streets were deserted but for knots of protesters, double lines of police and harried commuters seeking rides home. Tear-gas fumes penetrated even the sparsely populated stations of the subway.

Four persons were reported wounded last night when troops opened fire on a stone-throwing crowd in southern Santiago. This afternoon, a student was shot in the head when police stormed a university building where medical students were demonstrating.

Eight persons died, and more than 2,300 were reported arrested in the three previous national protests beginning last May. Today, opposition groups, including a newly formalized coalition of political leaders called the Democratic Alliance, called only for peaceful demonstrations and the banging of pots and pans by citizens in their homes.

However, violent street protests were promoted for both days and possibly tomorrow by leftist groups, political sources said.

The varying protest plans reflected an increase in tension within the opposition centrist sectors led by the Christian Democratic Party. Communist leaders had been excluded from the Democratic Alliance, and some leftists are reported to be increasingly reluctant to accept the coalition's proposal for returning Chile to democracy.

In an effort to head off violent protests in poor neighborhoods, government security forces worked door-to-door this week delivering warnings against opposition. In a complaint filed in court yesterday, several shantytown residents charged that police told them that if they burned barricades in their streets, their houses would be burned down.

In a communique yesterday, the government said that "all disturbances of the public order" or property damage would be "the exclusive and absolute responsibility" of the protest organizers. In a short statement, Pinochet also warned that opposition leaders "would suffer the consequences" of any disturbances, "even though they say the protest is peaceful."

The political significance of the new demonstrations was heightened by their timing within a few days after new initiatives by the government and the opposition. Both sides designed proposals to win over the middle-class and conservative sectors, which are believed to hold the balance in an increasingly polarized society.

Last Saturday, Christian Democratic Party leader Gabriel Valdes issued a statement supported by the Democratic Alliance calling for Pinochet's resignation and an 18-month transition to civilian government. The 27-page declaration represented the first major effort by opposition leaders to define the protest movement publicly as an effort to end Pinochet's rule.

The strong government response to the demonstrations, meanwhile, contrasted with Pinochet's inauguration of a new Cabinet, described by government spokesmen as a move for liberalization.

The civilian-dominated team is headed by Sergio Onofre Jarpa Reyes, an ambitious politician who once served as president of the conservative National Party. Jarpa, known as a fervent nationalist, left his position as ambassador to Argentina for the Cabinet post and is reported to have prepared broad plans for easing pressure on Pinochet with moves toward democracy.

Progovernment newspapers have reported in recent days that the government now will allow thousands of political exiles to return to Chile, and will draw up a specific timetable for a transition to democracy.

However, neither Pinochet nor Jarpa promised these or other specific liberalizations in remarks last night and today. Pinochet said in a short speech last night that "decisive steps" would be taken but that he would not announce details until next month, when the government will celebrate the 10th anniversary of the military coup that overthrew socialist president Salvador Allende.