The "black Saturday" that struck this dusty port city last June with the worst rioting in the 20-year reign of King Hassan II has underlined the desperate economic conditions of much of Morocco's population and cast a dark shadow over the future of the monarchy.

The government has said that 66 people were killed and 100 injured in the orgy of stoning, burning and looting touched off June 20 by a general strike against rising food prices. Opposition leaders, meanwhile, have estimated the dead at 637, and charge that many were killed by police and Army gunfire.

Those figures, and the more than 2,000 arrests that the government acknowledges, have posed the question of whether Morocco's government is capable, amid the growing economic distress, of sustaining its class-bound domestic rule or its costly military operations against the Polisario guerrillas in the Western Sahara.

Some of the rioters were heard shouting that "the government takes our bread to pay for the Sahara." And one high government official said privately, "It was a class riot, which took on political overtones -- basically, an expression of the rage of the poor."

Courts here and in the capital at Rabat have been handing out hundreds of stiff prison sentences against the rioters, while acquitting some people. Meanwhile, Abderrahim Bouabid and other leaders of the Socialist Union of Popular Forces and its associated trade union are threatening to withdraw their 16 deputies from the 164-member parliament when it opens this fall.

Throughout his reign, King Hassan has insisted on maintaining the forms of a parliamentary, multi-party state. The opposition Socialists and Istiqlal Party, Morocco's oldest and largest nationalist party, charge this is largely a facade, intended to please the West -- especially France and the United States, which with Saudi Arabia are Morocco's biggest aid donors.

Withdrawal of the Socialists would crack this facade, the Socialists claim.

"Hassan does not want us to withdraw," says a Casablanca socialist leader. "He offers us our newspapers back and other 'advantages' if we agree not to boycott the parliament." Police occupied the party's newspaper offices June 20.

Symbols of wealth were the main targets of the riots in the city, where up to 60 percent of the labor force is now believed to be out of work. The government's figures show burning of 12 pharmacies (usually run by affluent women who have succeeded in a Moslem society where males dominate), 23 bank branches, three post offices, two tax-collection centers, seven gas stations, three clinics, 21 private cars and two buses.

Looted or damaged, says the government, were two industrial plants, two apartment buildings, three private homes, a municipal building, 54 private cars, 45 buses, two municipal guardposts and "several" shops.

Price increases were the immediate cause of trouble. They were announced May 28 and ranged from 14 to 77 percent on sugar, bread, flour, cooking oil, milk and other basic necessities. The increases were caused by cuts in government subsidies.

The subsidy cuts and resulting price increases were halved June 6, after stormy parliamentary debate and protests by the Socialists and even progovernment parties. However, the government of Premier Maati Bouabid, a former Casablanca attorney who once had socialist leanings himself, insisted that the price increases had to stand at about half their original size.

Morocco's normally progovernment labor federation, the Union Marocaine du Travail (UMT) joined that of the Socialists in demanding 50 percent wage increases and greater social security benefits to meet the steep rise in living costs.

The UMT called a general strike in Casablanca and nearby Mohammedia June 18. Many employes of national transport, utilities, and other enterprises walked off their jobs, and were joined by socialist workers and many shopkeepers and tradesmen.

Then, the Socialist Confederation called for another, nationwide general strike June 20, and the rioting followed.

The government version of "black Saturday" is that workers did not follow the order to strike on June 20, causing Socialist leaders to stir up the violence.

However, according to socialist leaders, police occupied their offices even before any violence began. They deny any incitation of the crowds and have demanded that a parliamentary commission investigate.

Beyond these disputes, meanwhile, analysts are pointing to deep underlying economic woes contributing to the rioting. Casablanca, Morocco's main commercial center, illustrates many of the Third World's worst problems of overpopulation, unemployment, undernourishment and under-schooling of the young.

"It was a miracle," says the French wife of a Moroccan, "that only two explosions like this have erupted since independence." The last, in 1965, began with student unrest over school conditions.

About half of the city's population is under 15 years old, and many younger children drop out of school. Masses of idle children and teen-agers swarm in the streets, like New York's Spanish Harlem or Lower East Side, but in greater numbers and in worse conditions of squalor.

Of 300,000 young people aged 15 to 20, only about 30 percent are in school, according to a study by Zakia Daoud, an editor of the Casablanca magazine Lamalif, which is close to the UMT.

Of those aged 20 to 24, only about 45 percent have jobs or are in college. Although half a million Moroccans once emigrated to find work in Western Europe and elsewhere, this migration has nearly stopped since 1978-79, when European states, hit by recession and unemployment, stopped admitting foreign workers.

Hunger in the countryside, aggravated by a two-year drought, drives over 1,000 people a day to the cities, mostly Casablanca. The urban population increases three times as fast as the rural one.

The World Bank, in its last comprehensive report on Morocco three years ago, found over 38 percent of the population below a $200-a-year "poverty line" income -- in a country where many necessities and luxuries cost much more than in the United States.

The same report made clear that Morocco's rich grow steadily richer, while the poor grow poorer.

"For all of these reasons together," said Daoud, "Morocco's cities are today powder magazines, and the biggest one of all is Casablanca . . . . Morocco must provide immediate satisfaction to its population in the present, since it can offer no projects for the future. There must be either ideology or bread. Best, in an underdeveloped country, would be to have both. Right now, we have neither."