Renewed demonstrations against the government of Gen. Augusto Pinochet shook Chilean cities today, leading to more than 550 arrests and two reported deaths and jolting a fragile effort by the government and its opposition to negotiate political peace.

Despite public pledges by political leaders and authorities to avoid violence, the fifth consecutive monthly demonstration against Pinochet's military rule provoked day-long incidents in Santiago between thousands of protesters and police using tear gas, clubs and water cannon.

Marches and clashes were also reported in in Concepcion, Temuto, Valparaiso and other major cities. Authorities confirmed tonight that one woman was shot to death by police in Valparaiso and a man was shot to death in Santiago. At least six persons were reported wounded.

Dozens of persons, including a protest coordinator who is the leader of the opposition Christian Democratic Party, were reported to have suffered injuries in beatings by police. Another Christian Democratic leader, former Sen. Patricio Aylwin, was arrested and later released.

The demonstrations reached a height tonight when thousands of persons marched through the streets of poor neighborhoods and built barricades to keep police out. Violent confrontations between police and demonstrators were reported in a number of neighborhoods, while in others residents limited themselves to peacefully banging pots and pans.

The new antigovernment demonstrations were scheduled three days before the Pinochet government's planned celebration of the 10th anniversary of the military coup against Socialist president Salvador Allende. They interrupted recent talks between Interior Minister Sergio Jarpa Reyes and the opposition Democratic Alliance, which includes the Christian Democrats and other parties, over a possible political solution to the growing confrontation between Pinochet and a mass protest movement.

The demonstrations in Santiago appeared to equal those of previous months despite a highly promoted initiative by Pinochet to relax his authoritarian rule. In the last month the government has authorized the return of more than 2,000 political exiles, lifted restrictions on the press and street movement and discussed further liberalization with opposition political leaders.

Following three days of violence last month that left at least 24 dead, the government also abandoned its use of troops and a curfew to repress street demonstrations today. Jarpa denounced the call for a national protest but said peaceful actions would be tolerated.

In Santiago, however, violence broke out at midday when more than 1,000 persons assembled around the traffic-congested Plaza Italia for a demonstration and sit-in planned by the Democratic Allliance.

Alliance leaders had meant to block a major traffic circle and marched down Santiago's Central Avenue toward the presidential palace. But when Genaro Arriagada, protest organizer and Christian Democratic party leader, sat down in the street with a group of protesters, he was beaten on the legs and body by police and forcibly moved.

Moments later, Aylwin, a former party president, was arrested and police began firing tear gas and jets of water from small tanks.

Militant students responded with rocks. For more than an hour afterward, more than 200 police battled with demonstrators around the plaza as opposition leaders unsuccessfullly sought to mediate.

Confrontations between police and demonstrators continued through the afternoon.

Tonight, Santiago authorities reported that 250 persons had been arrested in the capital before nightfall, but that all but two had been ordered released. More than 300 were reported arrested in other parts of the country.

The conflicts led opposition leaders to charge brutality by police and a rejection by Pinochet's government of its promise of accepting peaceful protest. "A violence is being turned loose that is unacceptable," said Gabriel Valdes, the leader of the alliance and president of the Christian Democratic Party.

Jarpa rejected the opposition charges and said the violence resulted because "those who organize demonstrations don't take responsibility for the consequences." He said tonight that fewer people had participated in the protest than in earlier demonstrations, and that the country was "on the road to greater normality." He called on alliance leaders to circulate in poor neighborhoods tonight to prevent further disorders.

The debate over the violence today continued this week's harsh public dialogue between opposition and government leaders over the protests and the government's progress in its political relaxation.

Jarpa and other government officials have said the new program is offering peaceful outlets for dissent and have criticized the opposition coalition for continuing to organize day-long national protests. The government maintains the protests have been dominated by extremist Marxist groups that more moderate leaders cannot control.

Today, government officials supported that charge by pointing to the slaying by security forces in shootouts last night of five alleged members of a leftist extemist group, the Revolutionary Left Movement. Another nine persons were arrested in raids that authorities said resulted in the capture of large stores of arms and evidence linking Revolutionary Left suspects to the assassination last week of the governor of Santiago, Gen. Carol Urzua.

Jarpa said in a press conference yesterday that citizens should organize defense committees in their neighborhoods to protect themselves against violence and added that if terrorist violence increased, "the answer" of the vigilante groups "will have to be in arms as well."

Opposition leaders, who have blamed security forces for deaths in previous national protests, sharply attacked Jarpa for his statements and warned that they are losing faith in the government's effort at negotiation.