Warning about the dangers of popular social networking sites such as Facebook and MySpace, Pope Benedict XVI has said that online communication between people must not stop face-to-face conversations.

"It is important to always remember that virtual contact cannot and should not be a substitute for direct human contact with people at all levels of our society," he said in a message to mark World Communications Day, which was released today.

He urged Roman Catholic bloggers and users of Facebook and YouTube not to trivialise the message of Christianity in pursuit of an online audience, the Telegraph reported.

"We must be aware that the truth which we long to share does not derive its worth from the amount of attention it receives," he said.

"We must make it known in its integrity, instead of seeking to make it acceptable or diluting it. It must become daily nourishment and not a fleeting attraction."

The 83-year-old pontiff, however, admitted that social networking sites offered the chance to make new friends and to spread the Gospel.

But, youngsters should not replace real friends with virtual contacts by excessively using the online forums, he said.

He called on Catholics to use the Internet in "a Christian way". "This takes the form of a communication which is honest and open, responsible and respectful of others," he said.

In his message, the Pope also admitted that the Vatican struggled to keep up with the demands of the Internet age, and that he still wrote in longhand.

Since being elected in 2005, the Pope has overseen a big increase in the Vatican's online presence. It now has a dedicated YouTube channel and its Pope2You.net portal gives news on the Pontiff's trips and speeches.

World Communications Day is on June 5 but the Pope's speech was made public on the feast day of St Francis de Sales, patron saint of journalism.