Choirs sang in the cool Sunday morning as family members laid flowers at tombstones of the victims of the 1960 Sharpeville Massacre.

On that Sunday 50 years ago, 69 unarmed people were killed and hundreds wounded when police fired into a crowd of 5,000 black South Africans.

They had gathered at the police station of the impoverished town south of Johannesburg to protest pass laws that restricted their movements.

A similar demonstration in Langa, near Cape Town, was also violently suppressed.

Deputy-President Kgalema Motlanthe told the crowd the incidents changed the nature of the anti-apartheid struggle.

"The Sharpeville and Langa massacres were a tipping point in that they served to trigger off deep revulsion and disgust, both locally and internationally, against the apartheid government," he said.

The incidents brought the banning of liberation movements such as the Pan-African Congress, which organized the demonstration, and the African National Congress. It also led these groups to abandon non-violence and take up arms.

The demonstrators were protesting laws that required them to carry pass books at all times or risk arrest. Many burned their pass books and offered to be detained. Instead, police, overwhelmed by their numbers, shot into the crowd.

The incident brought international condemnation, the beginning of the regime's diplomatic isolation and annual demonstrations in South Africa that often were violently suppressed.

Six years later, the United Nations proclaimed the Sharpeville anniversary to be the International Day for the Elimination of Racial Discrimination.

After the end of apartheid in 1994, the new government proclaimed the date South Africa's Human Rights Day and made it a national holiday.

Sharpeville, 50 years later, is still poor. Many residents live in shacks without running water or indoor sanitation.

Last month residents burned tires in the streets to protest what is called the lack of service delivery and local politicians whom they accuse of corruption. Such demonstrations have become frequent in a country with one of the widest gaps between rich and poor in the world.

Deputy-President Motlanthe said to adequately commemorate the victims of the anti-apartheid struggle, government must work harder to improve the lives of those who have not benefited from it.

"This means as government working with our social partners, we must strive to improve the quality of life of all our people by providing shelter, basic amenities, education and security," he added.

But he urged citizens to avoid violence and to voice their grievances through democratic institutions. He noted that poverty eradication, health and education are top priorities of the government of President Jacob Zuma.

Mr. Zuma did not attend the ceremonies. He was in Namibia to mark the 20th anniversary of Namibia's independence.