Desmond Tutu, South Africa's anti-apartheid icon, Nobel peace laureate and a man dubbed the "moral compass of the nation," marked his 90th birthday Thursday with a rare public appearance.

The jovial Tutu, who has long spoken out against injustice, attended a special thanksgiving service at St George's Cathedral in Cape Town, where he was appointed South Africa's first black Anglican archbishop.

The service opened with a rendition of "Happy Birthday".

Ninety years: Desmond Tutu attends a birthday celebration service in Cape Town
Ninety years: Desmond Tutu attends a birthday celebration service in Cape Town AFP / RODGER BOSCH

Tutu, looking healthy and wearing his trademark purple shirt and white collar under a black suit, waved in acknowledgement from a wheelchair.

He sat next to Leah, his wife of 66 years.

"This is a great day. You are with us despite all the many challenges over the years. Ninety years!" said Allan Boesak, a fellow anti-apartheid activist and clergyman who led the service.

July 10, 1985: Tutu speaking at the funerals of four young anti-apartheid activists killed by hand grenades
July 10, 1985: Tutu speaking at the funerals of four young anti-apartheid activists killed by hand grenades AFP / GIDEON MENDEL

"If some people had their way, you would have been dead already... their wish would have been just for Desmond Tutu to be gone and to shut up or be shut, but here you are," Boesak said in a fiery sermon.

During an online conference in the evening, the Dalai Lama expressed his "deep admiration and respect" for his "elder brother in the spiritual field".

"I believe in life after life, he believes in his creator. We often joke he will go to heaven, I might go to a very different place," the Dalai Lama said over video link.

October 14, 1997: South Africa's then foreign minister, Pik Botha, shakes hands with Tutu as he arrives at the Truth and Reconciliation Commision
October 14, 1997: South Africa's then foreign minister, Pik Botha, shakes hands with Tutu as he arrives at the Truth and Reconciliation Commision AFP / Odd ANDERSEN

"Please still live long, the world needs you as a good example."

Hollywood actor Samuel L. Jackson praised Tutu as a man able to stand up "to your oppressor while maintaining a sense of humour".

October 14, 1997: South Africa's then foreign minister, Pik Botha, shakes hands with Tutu as he arrives at the Truth and Reconciliation Commision
October 14, 1997: South Africa's then foreign minister, Pik Botha, shakes hands with Tutu as he arrives at the Truth and Reconciliation Commision AFP / Odd ANDERSEN

Tributes and well-wishes for the revered anti-apartheid icon poured in from around the world, with many on social media sharing a video of Tutu dancing with the Dalai Lama on the latter's 80th birthday.

President Cyril Ramaphosa in a statement lauded Tutu "as a fighter in the cause for human rights, for equality and for social justice" throughout the 59 years since his ordination.

The line-up of speakers at his birthday is a reminder of Tutu's values, surrounding himself with rights advocates
The line-up of speakers at his birthday is a reminder of Tutu's values, surrounding himself with rights advocates AFP / Fabrice COFFRINI

He paid tribute to "The Arch," as Tutu is fondly called in South Africa, "for a life that has been well-lived in honesty, integrity, fearlessness and service to humanity."

US President Joe Biden said he was "inspired by his personal commitment to championing human rights and to always speaking out for what is right."

"The world has continued to learn from Archbishop Tutu's message of justice, equality, and reconciliation," Biden said in a statement.

A tireless activist, Tutu has in recent years slammed even the ruling African National Congress (ANC) -- the vanguard of the fight against white-minority rule -- for cronyism and nepotism after apartheid ended in 1994.

In the past, he has confronted homophobia in the Anglican Church, challenged Nelson Mandela over generous salaries for cabinet ministers and stridently criticised the corruption that mushroomed under ex-president Jacob Zuma.

"At times when we have found ourselves losing our way, you have taken us well to task," said Ramaphosa.

"For nearly three decades, yours has been a voice of conscience, guiding us and motivating us to do better by our people," he said.

Ordained at the age of 30 and appointed archbishop in 1986, Tutu lobbied for international sanctions against apartheid, and later for human rights on a global scale.

He turned his focus on the thorny issue of reconciliation in the post-apartheid era as head of the Truth and Reconciliation Commission.

He retired in 2010 and rarely appears or speaks in public now.

He was last seen in public in May, when he and his wife got their Covid-19 vaccinations.

Tutu was diagnosed with prostate cancer in 1997 and has undergone repeated treatment.

His successor, Archbishop Thabo Makgoba told AFP that Tutu "was so fed up with today's democratic government".