ZAIRE; An African nation rich in natural resources but plagued by political instability and economic stagnation

Zaire could rank among the richest nations on earth. Its natural resources are immense. It is the world's largest exporter of industrial diamonds and cobalt. Its huge lakes abound with fish and hydroelectric potential, and its forests could provide raw material to paper mills or furniture factories for decades.

But since independence in June 1960, Zaire has been plagued by political instability, a lack of trained manpower, and a huge foreign debt.

Travelers arriving in Kinshasa, the capital city, are struck by the tens of thousands of inhabitants wandering along the city's avenues. Many of them are unemployed. All day long they palaver and look for part-time jobs to help them get by.

In the last 24 years the population of Kinshasa has exploded from 500,000 to 3 million inhabitants. Most of the city's new residents are former peasants who have been attracted to urban life.

Only after they have reached the metropolis do they realize that electricity and running water are not free and that jobs in government agencies or industries are in limited number.

Nowadays Kinshasa looks like many other black African cities. Its downtown skyscrapers are surrounded by endless neighborhoods where entire families cram into tiny, single-room houses made of gray concrete blocks. Only the main avenues are paved. There are no sewers.

Ironically enough, those who have chosen to remain in the countryside now are better off. A Roman Catholic missionary explains, ''They live in huts, grow vegetables, and breed their own livestock. The ups and downs of the industrial economy are unknown to them.''

In July this year, a few days after his third reelection to the presidency of his country, Mobutu Sese Seko acknowledged that the economic situation of his fellow citizens was bad. But he praised himself for having in less than a year reduced the country's foreign debt from $5 billion to $4.2 billion.

Mr. Mobutu, a former journalist, has been in power for 19 years. His supporters say he restored the unity of the country after the bloody civil war that followed independence. His opponents criticize his autocratic way of ruling.

Indeed, Zaire's only authorized party, the Popular Movement of the Revolution , controls every aspect of political, social, and economic life.

Many opponents have been executed. Others are in jail, and international human rights organizations say they are often tortured.

President Mobutu has also come under sharp criticism for alleged misappropriation of state funds. He has amassed a large fortune but contends he doesn't get more from Zaire's state coffers than his annual endowment voted by parliament. Foreign diplomats in Zaire's capital say this represents approximately 10 percent of the entire state budget.

After a series of deflationary measures announced by the Zairean government in September 1983, prices for basic commodities rose by 30 to 40 percent while salaries remained unchanged. This further reduced the standard of living of the average Zairean. A schoolteacher in Kinshasa, for example, makes $13 per month. A civil servant with a university diploma, earns $25 per month.

''With such salaries,'' a Western diplomat explains, ''you can't make both ends meet. To survive most Zaireans make ample use of what is known here as Article 15.'' In clearer terms this means many Zaireans give way to corruption: teachers sell diplomas. No official form is available from a civil servant without a tip.

Zairean officials say what their country needs the most is a transportation network that would link Kinshasa to the main provinces of the country. But they realize that this would require huge investments - something considered unlikely under present circumstances.

Moreover, Western diplomats say the shortage of skilled workers in the country would make it very difficult for the Zaireans to maintain highways and railways.

For several years to come, most of Zaire's copper exports will have to be shipped to Europe via South African ports. And crops will continue to rot in the eastern province of Kivu while many fruits and vegetables sold in Kinshasa's markets are imported from South Africa.