Hundreds pack into a small square outside of Rome to hear an address by Pope Francis.

A rousing ovation greeted the pontiff as he emerged from his sprawling summer retreat in Castelgandolfo.

He offered a prayer to mark the 70th anniversary of the massacre of tens of thousands of Poles during World War Two.

He also said he was looking forward to an impending trip to Brazil, where millions of Catholics are expected to gather for World Youth Day.

"Let us pray for this pilgrimage that is about to begin," he said.

It will be Francis' first foreign trip since he was named head of the Catholic church earlier this year.