VATICAN CITY – Pope Benedict XVI put church leaders on notice Thursday, saying social networking sites such as Facebook and Twitter aren’t a virtual world they can ignore, but rather a real world they must engage if they want to spread the faith to the next generation.

The 85-year-old Benedict, who tweets in nine languages, used his annual message on social communications to stress the potential of social media for the church as it struggles to keep followers and attract new ones amid religious apathy, competition from other churches and scandals that have driven the faithful away.

Archbishop Claudio Maria Celli, head of the Vatican’s communications office, cited a 2012 study commissioned by U.S. bishops that found that 53 percent of Americans were unaware of any significant presence of the Catholic Church online.

Other studies, Celli said, made clear that the “millennial generation” of people born after 1982 use Facebook, Twitter and YouTube far more than their parents as primary sources of information, entertainment and sharing political views and community issues.

“The digital environment is not a parallel or purely virtual world, but is part of the daily experience of many people, especially the young,” Benedict said. “Social networks are the result of human interaction, but for their part they also reshape the dynamics of communication which builds relationships: a considered understanding of this environment is therefore the prerequisite for a significant presence there.”

Benedict is a superstar online, with 2.5 million Twitter followers. And under his pontificate, the Holy See has greatly increased its presence online, with YouTube channels, papal apps and an online news portal www.news.va that gathers all Vatican information in one place.