Three weeks ago, as a red Datsun sped away into the darkness of downtown Lima, a bomb blew out the windows and glass dors of the U.S. Embassy. A short time later, in an apparently coordinated series of attacks, five more bombs hit American targets--first the backyard of Ambassador Edwin Corr, and then the buildings or warehouses of the Bank of America, Ford, the Coca-Cola Co., and the Berkemeyer Co., a Peruvian distributor for a dairy company connected to Carnation.

Neither Peruvian investigators nor U.S. officials know who threw the bombs -- apparently dynamite, judging from the scraps of dynamite paper found on the embassy steps--or why they singled out American institutions that night.

President Fernando Belaunde Terry, in a statement some of his own intelligence officers disagree with, has suggested that the bombers were drug traffickers angry about recent substantial U.S. aid agreements to help Peru fight drug traffic. A high-ranking Peruvian intelligence official said in a recent interview that the day of the bombing was Peru's annual day to honor the national Civil Guard.

"They wanted to play a nasty game with us, and what's most visible? The U.S. Embassy," the official said. "It's not a terrorist act like the rest of them. This was special, to attract attention -- and they got it."

Just who "they" are is a question that for over a year has bewildered Peruvian citizens, frustrated public officials and helped generate more than a little concern about the staying power of the country's latest democratic government. Throughout the first year of his presidency, which began in July 1980 after 12 years of military rule, Belaunde has been confronted with so many bombing and sabotage attacks that nearly every day's newspaper seems to carry news of a violent assault somewhere.

From August 1980 to August 1981, Peruvian officials recorded more than 300 dynamite bombings of public buildings, plazas, power stations and private businesses. They list another hundred molotov cocktail attacks and 350 cases of what they call "white terrorism"--nondestructive acts ranging from telephoned bomb threats and explosives robberies to the sudden running up of a hammer-and-sickle flag on a public flagpole. In one recent case, unidentified people took over a radio station late at night long enough to slip on the air a cassette tape that exhorted Peruvians, in Spanish and the Indian language Quechua, to resist their oppression and understand the need for armed struggle.

So far the only apparent injury in the attacks has been one bomber who was said to have injured his hand when his bomb blew up early. The Marine guard on duty at the U.S. Embassy was lucky enough to have been bending down behind a recently installed bulletproof glass screen when the embassy was attacked, so he escaped what might otherwise have been a deadly spray of flying glass. The bomb that went off in Corr's back yard did nothing more serious than wreck the garden furniture.

"The terrorist attacks in Peru are more against property than against human beings," Belaunde said in an interview not long before the embassy bombing. "That is why I am not as worried as many other people. For instance"--referring to the shooting of Pope John Paul II--"in Rome I suppose they are quite worried. If in the Eternal City, in St. Peter's Square, in the Bernini colonnade, if you have the maximum type of terrorist--well, it seems we are not in such bad shape in Peru."

The oddest part about the attacks is that nobody ever takes responsibility for them--no boasting telephone calls, no letters to newspapers, none of the usual calling cards of urban terrorists.

"You don't have a nationwide high-powered terrorist organization going," one diplomatic observer said. "The chances are that somebody would have found it if it were around, or that they would take credit for" the attacks.

The only political group to have been singled out in the assaults is an apparently tiny Maoist organization called Sendero Luminoso, which means "shining path." The intelligence official interviewed said that of the 400 persons who had been picked up in attacks of this nature, many had identified themselves as members of Sendero Luminoso.

"Sendero Luminoso has set out to make problems for the government, to destabilize it a little bit," he said. "It's very rudimentary. They're not very technical. They just use dynamite. There's no electrical apparatus, there's no plastique . . . . They're not even choosing their sites. It's just wherever they happen to be." In some cases, he said, arrested bombing suspects were carrying written plans that they had executed incorrectly.

Dynamite is not difficult to get in Peru, which is a major mining center, and Belaunde is among those who have suggested that Sendero Luminoso may not be responsible for all or even most of the attacks.

"It is done by groups of people that are paid by somebody," he said. "I suppose there are some international interests. Leftists--there may also be some extreme reactionaries. You know, we do not satisfy reactionary people. It could be one or the other."

Belaunde's new government has had a fairly grueling first year, much of it taken up with economic problems and labor disputes. At one point in August, when many Peruvian labor contracts are traditionally renegotiated, all the city's bank employes and public health doctors were on strike at once.

Many of those strikes have been resolved, although the Peruvian economy is far from healthy. Despite the military's steady pressure for more money, stronger laws and a freer hand in hunting down bombers and those the military sees as subversives, neither the economic disruption nor the bombings seem to have seriously threatened the new civilian government.

"If you really wanted to create chaos in a major way, you'd go for major targets," said a young Peruvian economist. "It seems a calculated attempt to create a certain disruption, a certain uneasiness, but almost no one pays any attention to it."