Pope Francis has turned 80 and the world's news media carried the news of his birthday as if he was a celebrity, which he is.

He had hinted after his inauguration that he would retire from his duties if he could no longer fulfil them, but there are no indications from the world at large that he should retire from his duties as must members of the electoral college of cardinals who elect.

Birthday greetings poured in from the mighty and the less mighty and Francis responded by saying: "I thank you all for your kindness. Please do not forget to pray for me."

The greetings arrived from everywhere via new and old communications' means including tweets with the hashtag #Pontifex80, The Associated Press reported.

The Pope shared his birthday breakfast with eight homeless people before celebrating Mass with some cardinals.

U.S. President Barack Obama said Francis "has inspired people around the world with his message of compassion, hope and peace."

Italian President Sergio Mattarella recalled that the Pope has called on Europeans to show solidarity with the less fortunate, in particular "migrants and all those who live at society's margins."

PRISONERS SENT POPE BIRTHDAY GREETINGS

The Vatican reported that Pope Francis received some very special birthday wishes from prisoners detained at the Due Palazzi prison in Padua, Italy.

The prison chaplain, Don Mario Pozza, arranged a skype call with the Pope involving some 60 prisoners, several guards, the prison warden and volunteers, at about 5 p.m. Rome Time on the afternoon of the pontiff's birthday.

One prisoner identified as Marzio read a letter to Francis in which he promised prayers for the Pope, and said, "Thanks from the bottom of our heart for your daily witness, which nourishes our hopes and our dreams, and gives us continuous glimmers of light."

Welcoming the greetings, Pope Francis said, "I thank you all so much for your tenderness, your closeness – and I ask the Lord to bless you – may the Lord bless every one of you: your families, your parents, your brothers and sisters, your children."

Nigerian Bishop, Emmanuel Adetoyese Badejo of Oyo Diocese and president of the social communications committee at SECAM, a grouping of African bishops, was one the many well wishers for Francis on his Dec.17 birthday.

"The African church deeply appreciates the Holy Father's apostolate on marriage and love in the family and pledges to stand firm for the integrity of Christian marriage and the family at all times," said the bishops.

Columnist Paul Vallely wrote a tribute to in a Guardian newspaper opinion piece titled, "For God's sake Pope Francis, don't retire. The world needs you."

"Pope Francis is 80 on Saturday – the age at which cardinals must retire from the electoral college, which will choose the next leader of the world's 1.2 billion Roman Catholics," wrote Vallely.

"Will Francis also go at 80? In the past, popes ignored the watershed. They went on until they died. But Benedict XVI changed things when he became the first leader of the Catholic Church to resign in more than 500 years. Francis has indicated that he might retire too. It is vital, not just for the church but the world, that he does not."

He said the two popes before Francis were conservatives and John Paul II and his successor, Benedict, "set the public tone of Catholicism for more than three decades".

"In just three years, Francis has gone some way to hauling the church back towards the center. But the ideological right is increasingly fighting back.

"Their private criticism of the first pope from the global south is turning to public dissent. Now is not the time for Francis to have innovative thoughts about institutionalising papal retirement by stepping down," asserted Vallely.

As Pope Francis celebrated his 80th birthday, World Council of Churches general secretary Rev. Olav Fykse Tveit sent a greeting expressing gratitude for the steps the Pope has taken to foster the search for the visible unity of the church.

"I remember with joy your recent visit to Lund and the celebration of the journey from conflict to communion of the Roman Catholic Church and the Lutheran World Federation in which we could participate," said Tveit  in a greeting.

"You are speaking frequently from the unity on the way that grows when and where we pursue our journey as disciples of Christ together."