JOHANNESBURG — Heartbreak intruded on the opening day of the soccer World Cup when Nelson Mandela’s 13-year-old great-granddaughter Zenani was killed in an auto accident here early on Friday. In response, Mr. Mandela canceled a much-heralded appearance at a tournament depicted as a triumphant showcase for his country and his continent.
Zenani Mandela was returning home from the event’s Thursday night kickoff concert in Soweto, an extravaganza with stars like Alicia Keys and Shakira that was meant to launch the contest on a joyous note. At its conclusion, the sky lit up with fireworks as happy attendees made way to their parked vehicles.

According to police, Zenani died in a one-car accident on a Johannesburg highway. The man behind the wheel, who has yet to be named, was accused of drunk driving and may also be charged with culpable homicide, the police said.

The Nelson Mandela Foundation issued a statement saying the former president would now be unable to attend the opening ceremonies of the tournament.

The World Cup is being played in Africa for the first time, and the presence of Mr. Mandela, the frail, 91-year-old liberation hero, was expected to be an emotional highpoint to one of South Africa’s proudest days.

“We are sure that South Africans and people all over the world will stand in solidarity with Mr. Mandela and his family in the aftermath of this tragedy,” the statement read.

“We continue to believe the World Cup is a momentous and historic occasion for South Africa and the continent and we are certain it will be a huge success. Madiba will be there with you in spirit today,” the statement said, using a title from the Xhosa language by which Mr. Mandela is widely known.

Details of the accident remain incomplete. The Associated Press quoted a police spokeswoman, Edna Mamonyane, saying the driver was found to be drunk: “He lost control of the vehicle and it collided with a barricade.”

Zenani had turned 13 on Wednesday. She is the grandchild of Nelson Mandela’s daughter Zindzi.

Early reports said that Zenani’s great-grandmother — Mr. Mandela’s second wife, Winnie Madikizela-Mandela — had been in the car, but this was later denied. A family spokesman told the South African Press Association that Ms. Mandela, herself an iconic figure in the freedom struggle, was briefly hospitalized for shock after learning the news.

Statements of condolence to the Mandela family immediately began circulating. President Jacob Zuma said, “The nation shares your loss and mourns with you, especially on the day in which our dreams and hopes come alive in the opening of the first FIFA World Cup on African soil.”

The Mandelas might rightly be considered the nation’s first family. Mr. Mandela’s triumphs are well known to his countrymen, and so are his tragedies. His oldest child, Thembikele, died in a car accident in 1969. His second child, Makaziwe, died after living only nine months. His third child, Makgatho, died of an AIDS-related illness.

Zenani was one of Mr. Mandela’s nine great-grandchildren. She was the grandchild of Zindzi Mandela, the elder of two daughters born to Nelson and Winnie.

Winnie and Nelson Mandela divorced in 1996, ending a 38-year marriage that endured the persecution of apartheid and the separation caused by his 27 years in prison. In 1998, he married Graça Machel, the widow of the Mozambican leader, Samora Machel.

Even before the accident on Friday, there had been questions about whether his frail health would allow him to attend.

It was not immediately clear whether the tournament organizers would acknowledge the death in the pageantry of the opening day.

The cancellation of his appearance offered a sharp counterpoint to Mr. Mandela’s earlier and more vigorous years when, in a bold gesture as president, he saluted South Africa’s victorious team at the rugby World Cup in 1995, urging his countrymen — black and white — to support a squad associated by many black people with the Afrikaner elite of the apartheid years.

The opening ceremony Friday had inspired hopes for a similar transcendent moment, this time from soccer, the favorite sport of the nation’s blacks.

Mr. Mandela was freed from prison in 1990 and became president after the first democratic elections in 1994. In 1999 he stepped back from power, and his successor, Thabo Mbeki, was elected to office.

But Mr. Mandela continued to exert enormous influence both within and outside South Africa.

He played a central and persuasive role in lobbying for South Africa to host the tournament. In 2004, when international soccer authorities awarded South Africa the 2010 World Cup, Mr. Mandela said their decision was a perfect gift for his country 10 years after its first democratic elections.

Then 85, he held aloft the trophy and said he felt “like a young man of 50.”

The tournament is set to open Friday with a ceremony at a glittery new 90,000-seat stadium called Soccer City followed by its first game pitting low-ranked South Africa’s national team, nicknamed Bafana Bafana, or, The Boys, against Mexico.

In a letter to Mr. Mandela made public on FIFA’s Web site, Joseph S. Blatter, the head of the soccer governing body, said, “The entire football family mourns with you and your family, and today we stand by your side.”