A rally called to show support for the government of President Mobutu Sese Seko failed to draw a predicted massive turnout today.

The numerically small attendence called the Mobutu's support in his stronghold around the capital into question at a time when he is seeking to show government strength in the face of a rebellion in southern Shaba Province.

Billed in advance by local media as the biggest rally in Zaire's history, the rally filled little more than half of the 40,000-seat 20th of May Stadium, where Muhammed Ali and George Foreman fought 2 1/2 years ago. Many of those who came to the rally left early and Mobutu did not show up at the event, which was organized by the regional government on his behalf.

It was the second serious blow in a month to the government of this vast central African country, adding a new political dimension to its growing military troubles. For the past month, the serious threat has been in the south, where since March 8Katangan rebels of the Congo National Liberation Front have taken over a third of Shaba province.

Now there is evidence that dissidence has developed in Kinshasa, 1,000 miles from the fighting - and perhaps other corners of the country - with grave political implications for one of the closest U.S. allies on the continent.

Today's poor showing led to new doubts among local and foreign observers about the future of Mobutu.

The rally began at 10 a.m. when a few thousand people organized on the capital's main boulevard for a three-mile march to the stadium in sweltering heat. More joined the march along the way, but there were many more among the city's 2 million inhabitants who were conspicious by their lack of interest as marchers passed by.

The marchers - most organized by their businesses or local branches of Zaire's only political party, the Popular Revolutionary Movement (MPR) - carried banners along the palm-fringed streets declaring: "For Zarie we die," "MPR; Ready for Combat," "With Mobutu we will conquer," and "One people, one Guide." Mobutu is known in Zaire as the Guide.

On the government's allegation that the Angolan, Cuban, and Soviet governments are behind the current rebellion, other banners read: "Brezhenev - Castro - Neto: Paper Dragon," "Down with Soviet-Cuban Mercenary Activities."

One sign baffled several spectators. It said; "Zaire: Not to the Right, not the Left, nor the Center."

At the stadium, the response to the program - music by the Army band and an hour-long speech by Kinshasa Government Sakombi Inogo - was cool, with none of the interrupting applause or cheering that is customer here.

In one embarrasing moment, the governor shouted, "We will vanguish, victory," then threw up his arms as a gesture for cheers from the crowd. There was only silence. Sakombi repeated the cry in a louder noise, again throwing his arms upward. Silence again.

The governor, flanked by several Cabinet ministers, told audience of about 20,000 that the government wanted peace and stability, and that the Zaireans were innocent victims of foreign aggression. Sakombi added that the former Belgian Congo has lost 500,000 people during he rebellion after independence in 1960 and did not want further bloodshed.

Halfway through the governor's speech, the crown began to diminish.By the end, only, a few thousands remained to applaud politely.

Zairean journalists commented later that Africans in the Capital were discontent because of food shortages, corruption, unemployment and poor social services. Theysaid the population felt that Mobutu was to blame.