The government of Peru has begun the killing of 5,000 members of an officially protected herd of vicunas, drawing the wrath of international conservation groups and touching off an emotional national debate over policy toward this nearly extinct cousin of the llama.

At stake is the future of the rarest member of the camel family, adopted by Peru as its national symbol. A delicate and graceful resident of the high, remote reaches of the Andes, the vicuna is prized for its hide and soft, silky wool - which brings up to $100 a pound from fashion-conscious fanciers in the United States and Europe.

Government figures have put Peru's vicuna population at of 65,000," or more than 80 percent of the world total. Conservationists charge, though, that Peru has deliberately esaggerated its vicuna population so as to justify the "culling" of "unproductive" animals at the Pampas Galeras reserve 300 miles south of here.

Neighboring Bolivia has charged that Peru seeks to profit from the slaughter by exporting valuable vicuna skins.

"I see economic interests behind the Peruvians' actions," said Armando Cardozo, director of the Bolivian National Institute for Wool Improvement. Both Bolvia and tecuador have expressed interest in buying surplus vicunas from Peru to introduce into their own herds - ostensibly to save them from slaughter.

Peru has indicated that such sales would violate government policy, which deems the vicuna a "strategic asset" and estimates that the country's virtual monopoly on vicuna stocks eventually will generate $150 million a year in income for the financially pressed government once scheduled vicuna commercialization starts in 1981.

"If you had 80 percent of the supply of a certain resource and only three other countries had any of it at all, what would you do?" asked Antonio Brack, director of the Peruvian government's Special Project for the Rational Use of the Vicuna, "You'd want to bring maximum benefit from that scarce resource to your nation's economy."

So far this year, an estimated 1,500 vicunas have been killed at Pampas Galeras. Brack said park guards have been ordered to shoot the vicunas with .222 Remington rifles loaded with expanding dum-dum bullets.

Conservationists have charged that such methods of execution are unnecessarily cruel. But Brack said it was "the cheapest and most efficient way to dispose of the excess males and does the least damage to their skins" - worth $500 apiece and now in storage in government warehouses in anticipation of future commercialization.

Felipe Benavides, president of the Wildlife Fund of Peru, has attacked the policy of limited killing as "the most outrageous thing since the slaughter of baby seals." After a May visit here, Biran Davies, executive director of the International Fund for Animal Welfare, called Peru's program "one of the most brutal killings of wildlife ever."

Brack termed Davies' charges "a libelous insult to the national honor of Peru." He argued that the decision to kill 5,000 unattached male vicunas is "the most humane solution availabe," brought on by necessity.

The problem is one of too many vicunas grazing on too little land," said Brack during an interview in his office at the Ministry of Food and Agriculture here. "If we don't kill these 5,000 nonproductive males now, we could very well have 15,000 vicunas die of hunger between October and March of next year, including thousands of babies and fertile females."

Conditions at the 16,000-acre Pampas Galeras reserve have been aggravated by a three-year drought that has drastically reduced pasture areas, Brack said. He said grazing lands are also under pressure from sheep, cattle, llamas, alpacas and other domesticated animals that play key roles in the peasant economy of the high Andes.

To relieve the pressure on the land, Bneavides - who in 1975 was awarded the J. Paul Getty Wildlife Conservation Prize for his efforts on behalf of vicunas, guano birds, sea lions and whales - has suggested the animals be transferred to a second government reserve at Aguada Blanca, on the Bolivian border. Benavides said he has already raised the $150,000 that would be required for such a move.

But Peruvian officials have rejected this solution as both uneconomical and technically impractical. Brack claimed that as many as 50 percent of the vicunas would die during the 24-hour journey by truck from Pampas Galeras to Aguada Blanca.

"If these vicunas are not going to reproduce, why bother to move them?" Brack asked. "Moving them to Aguada Blanca does not resolve the problem of overgrazing, it merely transfers it to another area."

"Besides, we don't want their money," added Brack, who until this year was technical advisor to the Benavides group. "These are the same people who call us butchers and assassins after we've carried out one of the most successful wildlife resuce operations of all time."

Protected during Inca times by laws that made the killing of vicunas a capital offense and reserved the animal's coat for the nobility, Peru's vicuna population is estimated to have been 2 million at the time of the Spanish conquest. By 1965, however, less than 10,000 of the creatures remained.

Faced with the threat of the species' extinction, Peru and Bolivia signed a treaty in La Paz putting a 10-year moratorium on the killing or commercialization of the vicuna and its fur, hide or meat. The accord was later ratified by Chile and Agrentina.

Export of vicuna products has also been prohibited by the 1973 Convention on International Trade in Endangered Species, a treaty ratified by 51 countries. At the group's March conference, however, Peru attempted unsuccessfully to have the vicuna transferred from the endangered species list to a category that would permit limited commercialization.

Negotiations on the future of the La Paz treaty are set to begin Sept. 15, and Peruvian President Gen. Francisco Morales Bermudes last week announced a "temporary suspension" of vicuna killings in anticipation of the talks. Although Peru has expressed its willingness to consider extending the moratorium for another five years, it has indicated that it will press for major changes in the accord.

"The treaty did not forsee that the growth of the vicuna population would be so great," said Brack, who claims vicuna herds are increasing at the rate of 23 percent a year. "The current situation therefore threatens the very ends for which the treaty was established."

Instead, said Brack, Peru will set up plants locally to supply finished vicuna products to markets in Europe and the United States. By prohibiting the export of raw hides and unfinished wool, Brack said, Peru will be able to control killing and avoid the wide-scale contraband that conservationists have predicted will be an inevitable consequence of the vicuna's return to commercialization.