Protesters barricaded the streets and battled police as militants lit fire bombs and thousands of Chileans stayed home from work and kept children out of school today in a national day of protest against the government of Gen. Augusto Pinochet.

More than 200 arrests and a number of injuries were reported at the end of a day of demonstrations in Santiago and other major cities. Traffic thinned, many buses and trucks stayed off roads and schools' absenteeism was reported to range between 40 and 100 percent.

As night fell in Santiago, thousands of persons took to the streets in blue-collar neighborhoods to set bonfires, stone cars and barricade avenues. Throughout the city, residential areas echoed with horns and the din of banging pots and pans. Clouds of tear gas, fired by police, hung over the streets.

The government reported seven bomb explosions and three cases of arson last night and today. The fires destroyed two buses and damaged a movie theater in Santiago, where other vehicles were disabled by nails left in dozens of streets. Only minor damage was reported in the other incidents.

During the day, Chilean police appeared to show restraint and many protests proceeded peacefully. But scuffles and violence reportedly erupted late in the afternoon at the Federal Court building, where lawyers and other professionals were protesting, and at the teachers' campus of the University of Chile.

The protest, called by a coalition of opposition labor unions, was the second such event organized in the last two months and appeared to broaden what has become the most open political challenge to Pinochet in a decade of authoritarian rule.

The opposition coalition, dominated by Christian Democratic leaders and headed by the 21,000-member Copper Workers' Confederation, had called for economic reforms and a return to democratic rule. It promises to call national protests every month until Pinochet yields.

"For the immense national majority, the credibility of the government is absolutely null," said a statement issued by the National Command of Workers for the Protest. The demonstration, it said, "began the inexorable march of the people to the total recuperation of their dignity and full democracy."

Government officials, who had launched an extensive media campaign to head off today's protest, blamed the unrest on the Chilean Communist Party and the Soviet Union.

"Behind the organizers is the Communist Party and its known and permanent strategy of violence and subversion," Interior Ministry Subsecretary German Gardewezk told reporters here today. Nevertheless, he said activities in the country went on "with a most complete tranquillity and normality."

Pinochet, who blamed a Soviet conspiracy to overthrow him for last month's protest, left Santiago this morning for the town of Copiapo, 480 miles north. In a sharp speech there, he declared that "to the politicians I say from here that we are going to send them to their caves so this problem can end."

The protest movement, described by political leaders as the first to draw large numbers of average Chileans into open opposition to military rule, has developed after more than a year of economic crisis has weakened Pinochet's political support and previously firm hold on power. The May protest grew out of a canceled strike by the copper workers and was joined by Chile's major opposition party as well as students, professional groups, human-rights leaders and many citizens from all age groups.

Both last month and today, the union, led by 29-year-old Rodolfo Feguel, called on Chileans to stay home from work and school if possible, avoid purchases and business transactions and blow horns and beat pots and pans.

Today, these traditional Chilean forms of protest, reminiscent of the final months of the Socialist government of Salvador Allende overthrown by the military in 1973, were augmented by a number of demonstrations by students, human rights groups and neighborhoods.

More than 1,000 students gathered near the teachers' college library in south Santiago and built barricades of flaming pyres across nearby streets. Police in riot gear and circling helicopters fired tear gas and students responded by hurling stones. Preliminary reports by witnesses indicated that more than a dozen persons were injured.

At the end of the day, the Interior Ministry reported 58 arrests in Santiago. More than 150 arrests were reported in other Chilean cities by Chilean news services and human rights organizations.

In the capital, the protest intensified after dark as crowds gathered in residential areas to block streets with rocks, tires and other barricades. Police in buses and armored cars fired volleys of tear gas at gatherings.

Many commuters were stranded by the disappearance of buses. In San Borje, a large complex of stylish apartments across the street from the central government office building, residents created a deafening cacophony while flipping window lights off and on.

The demonstrations today came in spite of a series of government measures meant to neutralize the opposition movement.

In the last month, government officials have met with moderate labor and student leaders and Pinochet has announced the start-up of a progovernment "civilian military movement" to mobilize his supporters.