A priest has called the 'Charlie Charlie Challenge' "demonic activity", in an open letter warning his students against taking it.
In an open letter to pupils at the Saints John Neumann and Mario Goretti Catholic High School in Philadelphia, America, Father Stephen McCarthy said there was no way of knowing what could happen if they took the challenge.
The letter said: "There is a dangerous game going around on social media which openly encourages impressionable young people to summon demons.
"I want to remind you all there is no such thing as 'innocently playing with demons'.
"Please be sure to NOT participate and and encourage others to avoid participation as well.
"The problem with opening yourself up to demonic activity is that it opens a window of possibilities which is not easily closed."
The 'Charlie Charlie Challenge' trended on Twitter yesterday, as videos were posted of users taking the challenge, which involves balancing pencils in a cross, surrounded by the words 'yes' and 'no', in a rudimentary form of a Ouija board.
The challenge is supposed to have been an "ancient Mexican tradition", which supposedly summons a visit from a demon, which is indicated to be present by the movement of the pencils towards the word 'yes'.
Father McCarthy has been contacted for comment.