JOHANNESBURG, DEC. 13 -- Oliver Tambo, the ailing president of the African National Congress, received a tumultuous welcome from about 5,000 black South Africans today as he returned home after 30 years in exile.

It was Tambo's first appearance since a stroke last year left him partially disabled. He appeared frail, but smiled broadly as he waved to the wildly cheering crowd. He did not address the gathering. The stroke has affected his speech.

ANC Deputy President Nelson Mandela, Tambo's lifelong friend and former law partner, told the crowd that Tambo "wishes to say he is happy to be among you." He announced that the ANC president would address a rally Sunday. Tambo is expected to say only a few words.

Tambo, 73, who has undergone extensive treatment and rehabilitation in Britain and Sweden, arrived here to open a major ANC conference Friday, its first in the country since 1959. He will remain in South Africa a few weeks before returning to Britain for further treatment. He arrived on a charter flight via Lusaka and Harare, where he held talks with Zambian President Kenneth Kaunda and Zimbabwean President Robert Mugabe. Although Tambo is considered unlikely to remain ANC president much longer, his return was seen as symbolic of the transformation taking place in South Africa and the ANC's resurgence as the country's main black political movement. An editorial in the Johannesburg Star said Tambo's return "reflects the new start being made under President Frederik W. de Klerk, {but} also points to the tragedy of wasted lives which apartheid caused." The crowd chanted, sang, danced and waved colorful banners, saying "Welcome home Comrade President." At one point, some participants hauled down a South African flag outside the terminal and ran up the ANC's green, black and gold flag. Police quickly intervened and hoisted the national flag again.

Frequent clashes were reported between the crowd and a heavily armed police contingent. Scores of police with dogs patrolled the airport. Several people were reported bitten by dogs, and six were reported hospitalized.

Although less widely known than Mandela, Tambo is revered within the ANC. A low-key man known for his warm personal touch with colleagues, Tambo kept the movement together in exile after it was outlawed in 1960. He acted as roving ambassador, mustered international support and built it into the major vehicle for black liberation amid government efforts to crush it.

Tambo has played no active political role since his stroke in August 1989, although ANC members say he has been kept closely informed. Mandela has been de facto leader since he was released last February after 27 years in prison.

Sources close to the ANC say Tambo is likely to step down as president and be given an honorary title at its national convention in June. Mandela is expected to become president and a new deputy president is considered likely to be elected from the leadership's younger echelon. Such shifts would establish a possible line of succession in the movement that is bidding to form South Africa's first black majority government.

There has been speculation in the South African press that Tambo may step down at this weekend's conference. But James Stuart, an executive committee member in charge of organizing the conference, described this as "highly unlikely." More than 1,600 delegates are expected to attend the conference, including former exiles returning from 35 countries.