Pope Francis has said his predecessor as pontiff is having trouble getting around, but remains sharp of mind and memory, according to an interview published on Sunday.

"His mind and his memory are intact, perfect," Francis said of Benedict XVI in the remarks published by La Nacion.

He also praised the 89-year-old Pope Emeritus as a "revolutionary." Pope Francis said Benedict's abdication "exposed all the problems of the Church" and was itself "an act of government, his final act of government."

The interview was published five days after the current and former popes appeared together at an unprecedented Vatican ceremony celebrating the 65th anniversary of Benedict's ordination as a priest.