Chief Mangosuthu Buthelezi, leader of South Africa's 6 million Zulus, called Saturday for the unconditional release of jailed African National Congress leader Nelson Mandela.

He denounced the reimposition of the national state of emergency, extended for another year on Friday, and called for negotiation between black leaders and the white minority-led government."Black South Africa will not rest until Mandela is free," Buthelezi told a prayer meeting marking the jailed ANC leader's 70th birthday in the Natal village of Umlazi.

Buthelezi is known as a staunch critic of imposing sanctions to force change and is regarded as the powerful force among the 6 million South African Zulus, the largest black tribe in the nation.

Saturday was far from the first time he has called for the release of Mandela or condemned the policies of the South African government. His comments came a day after the extension of emergency rule and as rock stars from around the world staged a 10-hour concert to honor the ANC leader.

Meanwhile, supporters and critics of Archbishop Desmond Tutu scuffled Saturday during rival demonstrations before the black Anglican leader embarked on a trip to Moscow.

At least one black man, a supporter of Tutu, was taken into custody, and police ordered all members of the public to leave the main hall at Johannesburg's Jan Smuts Airport.

About 100 Tutu supporters remained in the hall and chanted Tutu's name when he arrived on a connecting flight from Cape Town.

Police and clergymen escorted Tutu and his wife, Leah, through the hall as his supporters, most of them black, cheered. Many white onlookers stared in amazement.

Mandela, who turns 70 on July 18, was jailed for life in 1964 on charges of sabotage. Despite international appeals for his release, he remains in a top-security section of Pollsmoor prison outside Cape Town.

President Pieter W. Botha has frequently said that Mandela can be released only if he denounces violence as the path to ending apartheid. Mandela has refused to renounce violence as a means to political power sharing.

"I say to the government that there is nothing to fear in releasing him," Buthelezi told tens of thousands cheering youths. "Every indication is there to help persuade the government that Dr. Mandela will first and foremost work for black unity."

Mandela was born as a prince and future chief of the Tembu, the largest tribe in the Transkei black homeland, but he rejected his right to the chieftainship. He was educated at a church school and a blacks-only college where his interests turned to politics.

The white-minority government repeatedly branded Mandela a communist but he denied it, saying he had always sought a non-racial society in South Africa.