In its latest attempt to keep up with the times the Vatican has married one of its oldest traditions to the world of social media by offering "indulgences" to followers of Pope Francis' tweets.

The church's granted indulgences reduce the time Catholics believe they will have to spend in purgatory after they have confessed and been absolved of their sins.

The remissions got a bad name in the Middle Ages because unscrupulous churchmen sold them for large sums of money. But now indulgences are being applied to the 21st century.

But a senior Vatican official warned web-surfing Catholics that indulgences still required a dose of old-fashioned faith, and that paradise was not just a few mouse clicks away.

"You can't obtain indulgences like getting a coffee from a vending machine," Archbishop Claudio Maria Celli, head of the pontifical council for social communication, told the Italian daily Corriere della Sera.