France announced yesterday that its forces have begun a phased withdrawal from Zaire's Shaba Province, raising the specter of an upsurge of rebel activity once the pullout is completed.

A Defense Ministry statement said elements of the 800-man French Foreign Legion force were being moved from the war-ravaged mining center of Kolwezi to the provincial capital of Lubumbashi, about 170 miles away. Officials said the pullout would be completed in 36 hours.

It was not clear how long the French force would stay at Lubumbashi before returning to its base on Corsica. Officials said that the stay in Lubumbashi was essentially for rest and recreation after a week of fighting.

The French announcement apparently caught by surprise Zaire's President Mobutu Sese Seko, who is currently in Paris and who conferred with French President Valery Giscard d'Estaing Wednesday.

Mobutu said at a press conference yesterday that he had heard the news about the French withdrawal from Paris radio. However, he refrained from criticizing the French leader and said that the French troops in Shaba Province would be replaced by an inter-African force.

Mobutu said five Moroccan units, whose size he did not specify, would soon join the 50 Moroccan military personnel already in Zaire. Other African countries that might send troops to Zaire were not named.

The Zairian leader said he would stop in Rabat to see the king of Morocco on his way back to Zaire. Mobutu is expected in Rabat Monday.

He is understood to have asked Giscard to keep the 800-man French paratrooper regiment in Kolwezi for the time being, perhaps as long as two months.

Apparently smarting from suggestions that France is trying to play gendarme in Africa, the French decided to bring the legionnaires home in matter of days. The regimental commander, Col. Phillipe Erulin, said in a French television interview that his troops had finished restoring security in the town of Kolwezi.

The French have apparently given up on the second part of their stated mission - trying to rescue missing Frenchmen thought to have been taken hostage. Defense Ministry officials expressed doubt that there was hope for any of them, and the Foreign Ministry issued a list of the missing.

In Brussels, the Congo National Liberation Front,.the exile political organization of the Katangan rebel invaders, said that the retreating forces had only taken seven prisoners, all of them French military men.

Another reason for the speedy French withdrawal may lie in the kinds of casualties the legionnaires would be likely to sustain if they remained to fight scattered guerrillas in the bush. Two legionnaires were killed Tuesday in an operation to clean out a nest of five guerrillas in an isolated village, according to military reports reaching Paris.

There are also complaints filtering back from the legionnaires that their unit is too small to handle security in an area as large as the region where the Katangan rebels were operating.

Mobutu said that half the regiment has already left Kolwezi for Lumbumbashi at the insistent request of Europeans there, which sought reassurrances that they would not be sujected to the same kinds of attacks as the Europeans in Kolwezi.

Mobutu said that the Europeans of Lubumbashi panicked when they heard the atrocity accounts of the European refugees from Kolwezi. French officials confirmed that large numbers of the Europeans in the provincial capital threatened to leave the country if they did not receive assurances of security.

Mobutu said there are 305 European refugees from Kolwezi waiting in Lubumbashi to return to the mining center to resume operations there once they get guarantees that it is safe to go back. Belgian industrial sources in Brussels are reported saying that under the best of conditions it will take six months to get the mines back into operation.

Mobutu said that Zairian copper production would be reduced to 150,000 tons from the usual annual rate of 450,000 to 480,000 tons.

He spoke at length of evidence of Cuban, Soviet, East German and Czechoslovak contributions to the Kantagan operation. At least some of the evidence he offered was greeted with skepticism here by Western officials with access to intelligence data. In seeking support from the West, Mobutu apparently feels it is in his interest to stress outside Communist influences over his opponents.

Mobutu claimed that the Katangans were organized into 12 companies led by a motorized Cuban company company commanded by a Capt. Marc Elino, attributing that information to radio intercepts. Mobutu also claimed that the overall command of the operation was in the hands of a Cuban general named Jose. Mobutu apologized for not having more details on his identity.

The testimony of the most highly qualified European refugees from Kolwezi, such as a French surgeon who spent the whole period of the Katangan operation on duty treating patients, rather than hiding, is that they saw or heard no evidence of the presence of Cubans.

Mobutu said that he had received the report of an American "special services" team that went to Kolwezi without his knowledge and performed autopsies on all of the European cadavers. He said the team found nothing but Soviet-bloc AK-47 slugs in the bodies examined.

An authoritative source said, however, that the only U.S. official who has visited Kolwezi since its recapture was a vice consul from Lubumbashi, who has filled reports to the U.S. Embassy the Zairian capital of Kinshasa.

Mobutu said that "an enormous stock of East German arms" was recovered in Kolwezi.

The Zairian leader said that on three occasions last year he had told President kenneth Kaunda of neighboring Zambia that there were Katangans in military tarining camps in his country but each time Kaunda replied that the only people being trained in the camps were Rhodesian nationalists.

"Now," said Mobutu, "he realized I was right." He called Kaunda "a friend or a false friend," and said he is not sure which he is.

Mobutu said that the Zairian general who was in charge of security for the Kolwezi region has been standing court martial since Monday for dereliction of duty.

Mobutu pleaded the difficulty of protecting a country almost five times the size of France with an inexperienced army of 45,000 or 50,000. He said the Katangan rebels had been infiltrating into the Kolwezi region for three months before their attack.

Despite Giscard's failure to leave French troops in Shaba, Mobutu went out of his way to thank him as Africa's only effective Western friend.