Pope Francis on Sunday became the first person registered for next year's World Youth Day festivities, using an iPad to sign up while addressing thousands of pilgrims and tourists in Saint Peter's Square.

"Thanks to this electronic device, I signed up as a simple pilgrim," Francis said, declaring himself the first person registered for next edition of the Youth Day celebration while flanked by two Polish youths.

The next edition of the global meeting of Catholic youths will be held next July in Krakow, Poland. It was most recently organised in Rio de Janeiro in 2013, shortly after Francis' election as pope.

Before digitally signing up for the event followed, the Pope appealed for the release of Italian Jesuit priest Paola Dall'Oglio, who was kidnapped in Syria two years ago.

In addition to calling for Dall'Oglio's liberation, Francis called for "renewed engagement by local and international authorities" to secure the release of all hostages being held.

Next year's event will be the 31st edition of World Youth day which was instigated in Rome in 1986 by Pope John Paul II, the first Polish pontiff who also served as Archbishop of Krakow.

It has since been held in countries on four continents.