Global leaders celebrate Desmond Tutu on his 90th birthday

South Africa's anti-apartheid icon and Nobel peace prize winner Archbishop Desmond Tutu marked his 90th birthday on Thursday.

Although frail, Tutu attended a service at St. George's Cathedral in central Cape Town, whereas the country's first Black Anglican archbishop had delivered sermons excoriating apartheid.

His daughter Mpho Tutu-van Furth said after the service she was "incredibly grateful" for her father's life which she said, "has definitely changed lives for so many of us."

Often hailed as the conscience of South Africa, Tutu was a key campaigner against South Africa's previous brutal system of oppression against the country's Black majority.

After South Africa achieved democracy in 1994, he continued to be an outspoken proponent of reconciliation, justice and LGBT rights.

"It was wonderful just to have a look at him," Anglican priest Lundi Joko said. "I mean 90 years is a blessing, it's a double blessing."

Tutu was awarded the Nobel Peace Prize in 1984 for his campaign of nonviolent opposition to South Africa's system of white minority rule.

After retiring as archbishop in 1996, Tutu was chairman of South Africa's Truth and Reconciliation Commission which investigated human rights abuses during the apartheid era.

Despite the serious nature of his work, Tutu brought irrepressible humor to his frequent public appearances.

Notably, he supported LGBT rights and same-sex marriage.