Mourners have been filing past the coffin of Archbishop Desmond Tutu, as his body lies in state at St George's Cathedral in Cape Town, South Africa.

Tutu, a Nobel Peace Prize winner who helped end apartheid in South Africa, died on Sunday aged 90.

His official state funeral will be held on 1 January after the lying-in-state period, allowing mourners to file past his body and say their final goodbyes.

Large crowds are expected to visit the cathedral over two days.

The lying in state period had to be extended to two days, "for fear there might be a stampede", a local priest told AFP news agency.

Priests burnt incense as Tutu's simple wooden coffin was carried into the cathedral.

Tutu's wish was that there be "no ostentatiousness or lavish spending" on his funeral and he even "asked that the coffin be the cheapest available", his foundation said.

Analyst Lukhanyo Vangqa tweeted that the coffin's simplicity was a "powerful rebuke" of the governing African National Congress (ANC) and its "emergent culture of opulence and decadence".

Tutu's eldest daughter Thandeka Tutu-Gxashe, accompanied by other family elders, walked slowly behind as the coffin entered his former parish.

His frail wife Leah had been wheeled into the church earlier.

A small service was held for the family before they viewed his body.

"It's a painful moment for Mama Leah. She is in bereavement. We need to pray for her. We need to love her and continue supporting her even though her beloved husband is gone," Archbishop Thabo Makgoba said.

Members of the public have been paying their respects to the much-revered churchman, a driving force in the struggle to abolish the apartheid system enforced by the white-minority government against the black majority in South Africa from the late 1940s until the early 1990s.

Human resources manager Amanda Mbikwana told Reuters news agency that she arrived as early as 05:00 local time (03:00 GMT) with her mother and nephews to bid farewell to Tutu, referred to by many South Africans as "Tata", or father.

"We have known Tata's work, he has stood up for us and we are here today in a free country to give him the honour, to celebrate his life and to support Mama Leah and the family," she said.

Memorial services have been held across South Africa while an intimate night of remembrance with his close friends is taking place.

After Saturday's funeral, Tutu's remains will be cremated and his ashes then placed in the cathedral, where he preached for many years.

The cathedral's bells have been ringing for 10 minutes every day at noon since his death.