South Africa on Monday began a week of mourning for revered anti-apartheid fighter Archbishop Desmond Tutu.

The Nobel Peace laureate passed away on Sunday at the age of 90, stripping the world of a towering moral figure and the last great protagonist of a heroic South African era.

His funeral will be held on New Year's Day at Cape Town's St. George's Cathedral, his former parish, his foundation said, although ceremonies are likely to be muted because of Covid-19 restrictions.

Dozens of people braved rain to gather outside the cathedral on Monday, leaving flowers and messages.

The widow of South Africa's first black president Nelson Mandela, Graca Machel, on Monday mourned "the loss of a brother".

Tutu "is the last of an extraordinarily outstanding generation of leaders that Africa birthed and gifted to the world", she said in a statement.

"He masterfully used his position as a cleric to mobilise South Africans, Africans, and the global community against the brutalities and immorality of the apartheid government," she said.

"He stood resolute and fearless, leading demonstrations cloaked in his flowing clerical robe with his cross as his shield -- the embodiment of humankind's moral conscience."

The bells of St. George's will ring for 10 minutes from noon each day until Friday. The church has asked those who hear the sound to pause in their daily work and think of Tutu.

A memorial service will be held in the capital Pretoria on Wednesday. Family and friends will gather on Thursday evening around Tutu's widow, "Mama Leah". 

On Friday, his remains will be placed in the cathedral on the eve of the funeral, although attendance at his farewell will be capped at 100, according to the archbishop of Cape Town, Thabo Makgoba.

Around 400 people have already expressed their intention to attend the event.

But Makgoba told a press conference: "Only a fraction of those who want to be there can be accommodated in the cathedral. So please don't get on a bus to Cape Town."

Music at the ceremony will also have to be moderated because of Covid curbs, officials said.

Tutu's remains will be cremated and his ashes will stay in the cathedral.

A truly meaningful life

Tributes poured in from across the globe, including from heads of state and religious leaders, with US President Joe Biden saying he was "heartbroken" by the news.

Barack Obama,  the United States' first black president, hailed Tutu as a "moral compass".

South African President Cyril Ramaphosa called Tutu a man of "extraordinary intellect, integrity and invincibility against the forces of apartheid".

Ramaphosa was expected to arrive in Cape Town on Monday, the presidency said.

Tutu's great friend the Dalai Lama said in a statement that "we have lost a great man, who lived a truly meaningful life." 

Church leaders in Cape Town said the Dalai Lama was expected to speak at Tutu's service, possibly by video link.

Anglican leader Archbishop of Canterbury Justin Welby said Tutu "was a great warrior for justice who never stopped fighting".

"When you were in parts of the world where there was little Anglican presence and people weren't sure what the Anglican Church was, it was enough to say 'It's the Church that Desmond Tutu belongs to'," Welby said in a statement.

The archbishop had been diagnosed with prostate cancer in 1997 and repeatedly underwent treatment.

He had been in a weakened state for several months and died peacefully at 7 am (0500 GMT) on Sunday, according to several of his relatives interviewed by AFP.

In his final years, Tutu's public appearances became rarer. This year, he emerged from hospital in a wheelchair to get a Covid vaccine, waving but not offering comment.