An Egyptian military team has arrived here to discuss aid - personnel and supplits - to help Zaire's army hold off Katangan rebels from penetrating further into southern Shaba Province, President Mobutu Sse Seko disclosed today.

Egypt is the second country to pledge backup troops for Zaire in a move to counter the growing threat to Zaire's valuable mining center, which virtually supports the rest of this massive Central Africa country.

Negotiations between the Egyptians and Mobutus senior military advisors is expected to result in the arrival of Egyptian troops within the next two weeks, according to diplomatic sources here.

The eiscosure followed within hours the arrival of the first contingent of Moroccan paratroopers - eventually to total 1,500 - in Kolwezi, the mining center believed to be the next target of the rebels. A second continengent of 250 is to arrive Sunday, and all are expected to be at "the front" by next Friday.

(Meanwhile, a report that South Africa has been secretly negotiating to aid Zaire in stemming the rebellion was denounced by South Africa's Foreign Minister Pik Botha as "complete nonsense," Reuter reported from Johannesbrug.)

News of the Moroccans' arrival came as Zaire's leader was showing the first signs of confidence since his troubles, the Katangan rebellion in the south and signs of political discontent around his stronghold in the capital, began on March 8.

Mobutu made his first public appearance since the rebellion began, and at least 100,000 people marched three miles then waited 2 1/2 hours in a tropical sun to hear him explain the Shaba situation.

The rally in the Twentieth of May Stadium was a complete reversal from the government rally last Sunday that all but fizzled. There was a festive atmosphere today as dancers, singers and musicians entertained the crowds. Last week about half of the small crowd began leaving after only 45 minutes.

Some observers questioned the crowd's motivation, however, since all businesses were closed for the event and employees were told they would not be paid unless they showed up for the march from Kinshasa's palm-fringed main boulevard to the stadium.

In a brief speech, Mobutu attributed the loss of one-third of Shaba to a plot within the army. Speaking in French and the local Lingala dialect, he explained that an unnamed high-level officer now under arrest had given the army cipher code to the Datangans, enabling the rebels to intercept messages and ambush military convoys.

Mobutu also said he was "ignoring" the role of Angola - Zaire's neighbor were the Katagans reportedly are based - because Angolan President Agostinho Neto was a pawn in the hands of the Soviet Union and Cuba, who he said are behind the "invasion."

"Angola today again denied incolvenment in the fighting which it said was being waged solely by the "Congo Liberation Army," news agencies reported. In Luanda, the Angolan Foreign Ministry denounced Morocco's intervention in what it called "a provincial rule" of Mobutu.)

Mobutu also offered the first specifics on the expulsion of Cuban diplomats last Monday. He said Zaire security officials had been aware of Cuba's involvement in the Katangan aggression for some time, but had been unbale to obtain proof until an incident at the village of Nguma, about 30 miles from the capital. He said that on April 4 a Cuban official, an embassy attache named Fernandez was caught with documentary evidence of Cuba's role. Mobutu did not outline the nature of the evidence.

Mobuto said he knew people had been laughing at Zaire. But he pledged that since the government is now able to insure the protection of its territorial integrity, Zaire's people would be able to laugh last and longest at their critics.

Foreign military support and today's rally clearly have made Mobuto feel his government is in a stronger position. His disorganized army now had backup from an experienced army, with more aid in the pipeline.