JOHANNESBURG (AP) — Police say Nelson Mandela's grandchildren underwent a harrowing ordeal with gunmen following the South African icon's 92nd birthday party.

No one was hurt and the attackers fled after an exchange of gunfire on Sunday.

Police spokesman Govindsamy Mariemuthoo said Mandela's grandchildren were returning to their Johannesburg home following the family birthday party.

Two gunmen approached the car as it entered the gates of the home of Mandela's daughter Zindzi and ordered the occupants to lie down in the entrance. One fired a shot and the family driver returned fire.

It was not immediately clear why police confirmed the incident Thursday. Armed car hijackings are common in South Africa, which has one of the highest rates of violent crime in the world.