Evening joggers along the beach front of this West African capital contribute to the city's aura of a placid Caribbean resort.

Gabonese President Omar Bongo, 47, promotes Libreville's vacationland veneer while running a tightly controlled political structure that oversees the liberal distribution of the country's oil-fueled affluence and that crushes with Draconian swiftness budding displays of even nonviolent dissent.

Significantly, the foundation of Bongo's rule dates back to the French influence here, one of the strongest ties France maintains with French-speaking, black African nations since they were granted independence.

It was French warships in 1849 that released African captives here after intercepting slave ships off the coast. The capital, Libreville or "place of liberation," takes its name from that history.

In 1964 Charles de Gaulle's clandestine Service d'Action Civique or SAC troops intervened to reinstall Gabon's first president, Leon Mba, two days after an Army coup. Bongo took power peacefully at Mba's death in 1967 and inherited a security apparatus run by generally right-wing SAC operatives and jobless former French Foreign Legion officers.

The French government's oil company ELF, which pumps 86 percent of Gabon's petroleum production, was influential in creating the existing security system and Bongo's 1,000-man presidential guard, headed today by former legionnaire Louis Martin, according to a senior western diplomat.

Socialist French President Francois Mitterrand has officially disbanded SAC, but, despite recent direct pressure from Paris, Bongo has refused to expel the former SAC agents and ex-legionnaires from his security service and circle of close advisers, the western diplomat said.

Yet, the ties between France and Gabon remain so close that Mitterrand's election in 1981 is credited with the outbreak of long dormant political ferment here by the opposition National Reform Movement, known as the Morena group. The Morena dissidents, according to western diplomatic sources, saw Mitterrand's election as a liberalizing trend in French politics that Bongo would be forced to follow by allowing them to form a legal opposition party. Under the amended Constitution, Gabon is a one-party state.

More than a year ago, the Morena members circulated a 17-page critique in Libreville of Bongo's virtual one-man rule and mailed copies to the French government. Their action was followed by arrests here, then by a peaceful political demonstration complete with dissidents waving placards demanding political freedom. But as many as 100 arrests were made by last spring.

At the end of November, 29 of those arrested were sentenced. Their terms ranged from 18 months to 20 years at hard labor for "threatening state security" and insulting Bongo.

The human rights organization, Amnesty International, appealed to Bongo to release the 29 sentenced dissidents. Two of the 13 prisoners given 20-year sentences, which include a former Cabinet minister, former ambassador to Egypt and the previous Omar Bongo University rector, "seemed to be in poor mental condition" after suffering harsh prison conditions, daily beatings and underwater submersion torture in their pretrial incarceration, Amnesty said.

In past public statements, Bongo has said that the multiparty system Gabon had at independence was "too divisive" given the country's small 900,000 population and numerous small ethnic groups. The multiparty system was at the root of the 1964 coup attempt, he has charged. His schedule was recently "too full," according to a presidential spokesman, to be interviewed by a reporter after the required submission of questions in advance.

On dissidents in general, Bongo said recently that "if there are certain socio-professional classes which, rightly or wrongly, feel hurt or forgotten, they must make use of the negotiating machinery at their disposal" in the Gabonese Democratic Party.

"They must be tolerant and they must make use of dialogue, which is always open to all," he said.

The now underground Morena opposition is widely considered to be based among the Fang, Gabon's largest ethnic group. Gabon's numerous minorities, like Bongo's own Bateke people, support minority ethnic control of the government out of fear of domination by the Fang, who make up 40 percent of the population. Thus Morena has been discredited by many as a serious political challenge.

"Bongo's government has a consensus of support among the minorities," said a western diplomat. "He would only run into serious trouble if he ran out of money."

Gabon--because of its small population, 150,000-barrel-a-day oil production as well as manganese, uranium and tropical wood exports--has one of Africa's highest per capita incomes, $3,000. It also pays civil servants one of the continent's highest yearly salary averages of $2,000.

"Bongo tries to spread the spoils around and is not really a ruthless ruler," said one western diplomat. "He is able to co-opt any potential challengers with high salaries and anyone Gabonese who wants a job gets a job."

The government is expected to have spent between $2 billion and $4 billion on the trans-Gabon railroad. The railroad, which is to be completed by 1988, is expected to open Gabon's interior for development of its rich mineral and tropical forest resources. Mitterrand is scheduled to inaugurate the 213-mile finished halfway point at Booue in mid-January.

Recently ELF and the American company, Amoco, discovered new offshore oil pools that will boost Gabon's slowly declining oil production and apparently help ensure Gabon's relatively healthy economic atmosphere and long-term political stability.