Former pope Benedict XVI, who retired last year, made a rare public appearance at a ceremony led by his successor Pope Francis in St Peter's Basilica to appoint new cardinals.

Pope emeritus Benedict, who lives in a monastery inside the Vatican walls and had sworn to remain "hidden from the world".

He joined the cardinals in the front row of the basilica for the ceremony to create 19 new "princes of the Church."

The elderly former pontiff, 86, seemed cheerful as he sat cloaked in his white papal garments in the midst of the red-robed cardinals, who have been selected by Francis to join the elite group responsible for electing future popes.

It is extremely rare to see the pope and former pope in the same location.

It is the first time Joseph Ratzinger -- who shocked the world in February last year by announcing his retirement as head of the Catholic Church -- has participated at a public ceremony in the basilica.

The new cardinals were presented with scarlet-red birettas and gold rings at a grandiose ceremony lead by the first non-European pope in nearly 1,300 years, who took over the reins from pope Benedict in March

19 of the cardinals come from South America, Africa and Asia.

Vatican observers say this should help correct a perceived bias towards European cardinals.

Sixteen of the 19 cardinals are under the age of 80 and can therefore take part in the secretive conclave that elects new popes from among their ranks.

Half of the cardinals are non-Europeans, including five cardinals from South America, two Africans and two Asians.

Pope Francis said in a letter to each new cardinal-to-be, according to La Stampa daily: "Becoming a cardinal is not a promotion, nor an honour or a decoration; it is simply a service which requires a broadening of the gaze and a widening of the heart."

The first non-European pope in nearly 1,300 years will bestow the honour of the red cap on the archbishops of Buenos Aires in Argentina, Rio de Janeiro in Brazil, Santiago in Chile, Managua in Nicaragua and Les Cayes in Haiti.

Aurelio Poli, 66, took over the post of Buenos Aires archbishop from Pope Francis, who was a regular visitor to the city's slums before he became pope almost a year ago.

Chibly Langlois, 55, will be the Church's first cardinal from Haiti, one of the poorest countries of the world.

For Africa, the new electors will be the archbishops of Ouagadougou in Burkina Faso and Abidjan in Ivory Coast, while Asia will be represented by the archbishops of Cotabato in the Philippines and Seoul in South Korea.

The pope's choices echo his desire to emphasis the pastoral side of the Church.

He chose for the most part leaders engaged with the problems affecting their local communities rather than favouring administrative heads.

Only four are members of the Curia - the Vatican's government - including Italian Pietro Parolin, 58, the new secretary of state, as well as German Gerhard Mueller, 66, who heads the Vatican's doctrinal congregation.

Among the most prominent in the group is Britain's Vincent Nichols, the 68-year-old Archbishop of Westminster.

He has been likened to Pope Francis for his determination to speak out for the marginalised.

Just a week before the Vatican ceremony, he waded into British politics to condemn welfare cuts.

He is best known for winding up the Church's conservative arm in 2010 by defending London masses for gay and transgender Catholics.

Gerald Lacroix, the lord archbishop of Quebec in Canada is one of the youngest electors to be chosen at the age of 56.

The oldest "new prince" will be Loris Francesco Capovilla, the 98-year-old former secretary to Pope John XXIII, who will not be attending because of his reduced mobility but is likely to receive his red cap at home.