Protests by university students have surprisingly and suddenly erupted in Brazil, where a tough, rightist military government usually does not allow such things.

Students demonstrators in recent days in at least half a dozen Brazilian cities have protested everything from bad food in university cafeterias to a general lack of freedom under the current government.

It had been widely assumed that government crackdowns and purges at colleges and universities throughout Brazil in the years immediately following the 1964 coup had crushed campus political activity. Education Minister Ney Braga, a former general, met today with his top advisers to determine how to deal with this unexpected outbreak of student revolt.

The president, retired Gen. Ernesto Geisel, has decided to leave the student problem in the hands of the Education Ministry and local authorities for the time being, a spokesman said.

The biggest demonstration took place yesterday in San Paulo, the nation's largest city, where about 10,000 students marched through the downtown area carrying banners reading: "Democratic Freedoms," "Amnesty", and "Free our prisoners." Leaders of the demonstrators, who represented several local campuses, read an "open letter to the people" that called for free elections and "an end to torture, arrests and political persecution." It also criticized "economic exploitation" and "the high cost of living."

Police kept the students in check with barricades and teargas, but there was no serious violence, and no one was arrested.

In other recent student demonstrations - in Rio de Janeiro, Porto Alegre, Belo Horizonte, Recife, Campinas and Ribeirao Preto - the police also have been careful to avoid violence.

The main reason for the Sao Paulo protest was the arrest last week of four workers and four students who allegedly belong to a pro-Communist organization called the Workers League.

The Sao Paulo students, in their open letter, responded by saying: "In this country today, anyone who speaks out for his rights is considered a subversive." Under Brazil's rigid national security law, the eight suspected leftists can be held for 30 days without being formally changed.