VATICAN CITY » The Vatican is offering indulgences for Facebook fans, Twitter lovers and other "virtual" participants of the upcoming World Youth Day in Rio de Janeiro — but there’s a hitch.

The Holy See’s social media guru, Archbishop Claudio Maria Celli, warned today that merely checking the pope’s Twitter feed won’t result in an indulgence, the ancient church tradition related to the forgiveness of sins that roughly amounts to a "get out of Purgatory free" card.

Rather, Celli told The Associated Press, a Catholic seeking an indulgence for participating in Rio — either physically or virtually — must truly be contrite and have a moment of deepening faith.

"When we are touching spirituality, the problem resides not in what I do but what is in my heart," Celli said. "It’s not just watching TV and the ceremonies of the Holy Father that I get the indulgence, or because I’m going to Rio, or because I’m reading a tweet of the Holy Father. That’s not the forgiveness of sins."

According to church teaching, Catholics who confess their sins are forgiven and therefore released from the eternal or spiritual punishment of damnation. An indulgence is designed to remove the "temporal" punishment of sin that may remain — the consequence of the wrongdoing that might have disrupted the sinner’s relationships with others.

Famously, Martin Luther’s opposition to the church’s practice of selling indulgences inspired him to launch the Protestant Reformation in the 1500s. He was excommunicated, and the practice of buying and selling indulgences has been illegal since 1562 Council of Trent, but the granting of them has continued.

The Vatican earlier this month announced, as it does ahead of every World Youth Day, that participants in the July 22-28 Rio edition would be eligible for indulgences. The criteria are tough: Catholics in Rio must go to confession, receive Communion, pray and "be truly contrite."

But in a blending of new technology with old theology, the decree approved by Pope Francis specified that even people who couldn’t make it to Rio could be eligible for a partial indulgence. The same conditions must be met, but sinners following the Rio event can score an indulgence by participating "spiritually" and following the events on "television, radio or, always with the necessary devotion, via new means of social communication."

During the last edition of World Youth Day in Madrid, in 2011, such partial indulgences were also available "to all those, wherever they may be," who followed the event from afar and met the same spiritual criteria. But the Rio 2013 decree spelled it out explicitly, evidence that the Vatican is continuing to appreciate the power of social media for its evangelizing mission.

To date, the pope’s @Pontifex handle has more than 7 million followers in the nine languages in which Francis tweets. Most of the followers signed up when Benedict XVI inaugurated the handle last year.

The Rev. Robert Gahl, a moral theologian at Rome’s Pontifical Holy Cross University, said the decree from the Vatican’s Apostolic Penitentiary was believed to be the first time that indulgences have been offered for social media participation.

"Some might falsely think that ‘Twitterized’ indulgences cheapen access to God’s grace. But they miss the point of the pope’s unprecedented move to social media," he said. "He is challenging tweeters to return to the sacraments of confession and Holy Communion and to deeply examine their conscience to free themselves from attachment to venial sins.

"The Pope doesn’t miss a beat or an opportunity to evangelize."