Rebel death adds fuel to charges that S. Africa out to destabilize Mozambique

New fuel has been added to the charge that South Africa is involved in efforts to destabilize neighboring Mozambique. A top commander of the Mozambique National Resistance (MNR) movement, Orlando Cristina, has been found dead in Pretoria. The South African police have confirmed Cristina was the victim of a shooting incident.

Cristina was described as the secretary-general of the MNR. His presence in South Africa will undoubtedly raise anew questions about Pretoria's relationship with the rebel movement.

The MNR has been fighting a guerrilla war against the Mozambique government of Samora Machel, which came to power in 1975 after a decade of war against Portuguese rule.

Allegations, along with what appears to be credible evidence, have mounted that South Africa has helped the MNR in its struggle.

The South African government has denied the charge, but earlier this year in Parliament, South African Minister of Defense Magnus Malan said support for the MNR could be forthcoming if Mozambique continued to harbor anti-South African ''terrorists.''

Mozambique support for the African National Congress (ANC), the main guerrilla movement of resistance to white rule in South Africa, is the key reason Pretoria helps the MNR, say analysts. Mozambique is a base for ANC raids into South Africa, and Pretoria has already made one major raid into Mozambique in 1981 against the ANC.

In its January issue, Africa Report magazine quoted senior State Department officials in the Africa bureau as saying the MNR receives ''the bulk of its support from South Africa.'' On Feb. 1, the State Department issued a report saying the statement reflected the situation as State perceived it.

Recent reports from Mozambique indicate the socialist government has been doing a better job of containing the MNR. Still, about one-third of the country seems to be affected by the MNR-government conflict.

South Africa has other interests in Mozambique besides routing the ANC. Ideologically, the two countries are at extreme odds. As a Marxist state, with 1 ,000-or-so military trainers and advisers from East bloc countries, Mozambique is one of the leading culprits in what Pretoria calls the communist ''onslaught'' against South Africa.

South Africa also watches Mozambique because of the socialist state's critical role in trying to help other southern African black states reduce their economic dependence on South Africa.

But the real key to reducing ties with South Africa is the transport sector. And Mozambique's Indian Ocean ports are vital to developing alternate transportion links.

The MNR made one of its most publicized attacks last December when it blew up oil storage tanks at the Mozambique port of Beira. Besides hurting Mozambique, this badly disrupted fuel deliveries to Zimbabwe. Analysts in Zimbabwe were convinced the attack was masterminded by South Africa because of its sophistication.

The MNR was apparently first supported by Rhodesia in the 1970s when black nationalists were fighting that country's white rulers with the support of Mozambique.