JOHANNESBURG, JAN. 11 -- American singer Paul Simon inaugurated the renewal of South Africa's cultural ties with the outside world tonight by holding a concert that had been threatened with violence by hard-line black nationalists.

No incidents were reported at the concert. However, the size of the crowd, estimated at between 20,000 and 30,000, was less than half the number expected, and its composition was nearly all white.

Fewer than 100 black demonstrators carried "Yankee Go Home" and "Paul Go Home" signs. They were outnumbered by 800 to 1,000 policemen standing by with armored vehicles and bomb-sniffing dogs.

Organizers blamed the absence of blacks in the audience on the political controversy surrounding the concert and threats of violence that made headlines in the local press. But blacks also complained about the high price of tickets, ranging from $15 to $30, and the location of the stadium where the concert was held in a downtown white neighborhood.

The local press hailed the concert, the first of five in four cities, saying it marked the formal end of South Africa's cultural isolation. The United Nations lifted its cultural boycott of South Africa last month -- a move urged by the African National Congress, the main opposition group here.

The ANC has strongly supported both Simon's tour and the arrival here of actress Whoopi Goldberg to film the South African black township musical "Sarafina."

At a reception here last night for both Americans, ANC President Nelson Mandela called them the most important artists to visit the country since the cultural boycott was lifted. He wished them "a real success indeed."

"I hope my presence here and the concerts will bring people pleasure as a musical evening and that for those few hours at least people can put aside their differences and simply enjoy the pleasure of the music," Simon said.

The Simon tour became controversial here after hard-line black nationalist groups announced their opposition to it just a few days before his arrival Tuesday. That night, hand grenades blew up outside the offices of two local entertainment companies involved in organizing the five concerts, and threats of violence to stop the tour followed.

The groups, led by the Azanian People's Organization and the Pan-Africanist Congress, said they opposed renewal of cultural contacts with the outside world -- which the Simon tour represented -- until South Africa was ruled by blacks.