Pope Benedict yesterday urged Roman Catholics not to commercialise Christmas, saying joy - not expensive objects - was the real gift of the season.

The 78-year-old Pope, apparently suffering from a sore throat, made his comments in an impromptu sermon during a visit to a parish in a densely populated neighbourhood on the outskirts of Rome.

"Joy is the real gift of Christmas - not expensive gifts that only cost time and money - but joy," he said, speaking in a hoarse voice.

"It is joy that should be communicated. We can communicate joy in a simple way, with a smile, a gesture," he said.

The congregation in the packed church broke into applause.

The German Pope, who will mark his first Christmas as Roman Catholic leader later this week, discarded his prepared text and delivered the entire sermon off the cuff.

It was the second time in as many weeks that the Pope warned against rampant materialism at Christmas. Earlier this month he said commercial "pollution" was ruining the spirit of Christmas.