South Africa began a nationwide day of prayer on Sunday, marking the beginning of a week of remembrance for Nelson Mandela, the country's first black president and an anti-apartheid icon, who died last Thursday, aged 95.

Hundreds of mourners from all races and religions thronged churches, mosques, temples and synagogues across the country, united in an outpouring of prayer and song for the man credited with leading the country's transition from white-minority rule to multi-racial democracy.

From a Methodist Church in Johannesburg, President Jacob Zuma implored South Africans to keep lit Mandela's flame of freedom and justice.

"He preached and practiced reconciliation, to make those who had been fighting forgive one another and become one nation," Zuma told a mixed race congregation of more than 1,000 worshippers.

"He preached and believed in peace, that we should live in peace, that we should live in unity."

"He was more than just an individual soul, he was the exposition of the African spirit of generosity ... He's only a reference and a marker to the better possibilities of our humanity," said Dean Michael Weeder of St George's Cathedral, Cape Town.

Pastor Niekie Lamprecht, of the Dutch Reformed Church, Pretoria East said: "May we as Christians in this Afrikaans church surprise the world by not responding with hate but with love and forgiveness. Mandela completed the journey. We thank God for this person in our history."

Mandela was jailed for 27 years on Robben Island by the white-minority racist regime which he opposed, emerging from prison in 1990 and becoming South Africa's first black president in multi-racial elections in 1994.

A year before he was elected president, he won a Nobel Peace Prize along with FW de Clerk, South Africa's last apartheid-era president who helped negotiate the end of apartheid with Mandela. 

In the Regina Mundi Catholic church in Soweto, noted for its place in the struggle against apartheid, parish priest Sebastian Rossouw called Mandela "a light in the darkness" and praised his capacity for "humility and forgiveness".