(newsweek) -- The poster was discovered on a Telegram app's pro-Isis channel by an intelligence group, and shows a terrorist with his face masked in white robes standing over the bloody severed head of the Pope.

“O Worshipers of the Cross, I swear to avenge every single drop of blood that you spilled and every house that you have destroyed,” reads a message scrolled across the top of the poster in white letters. “I swear that you will taste the bitterness of the cups of death and make your feasts massacres. You will not even enjoy living in your homes, Allah willing.”

The poster was discovered just days after the same group released another poster calling for an attack on the Vatican during Christmas. The messages seem to be timed to spark fear and dread among Christians just as they prepare to celebrate their most important holidays, experts say.

Just a day before Wafa released the picture of the pope’s beheading, another pro-Isis group released a cartoonish poster featuring a Santa Clause hat and beard.

“Just Terror Everyone, And a Terror Filled New Year,” reads a message in English spread on the pro-Isis telegram channel “Lone Mujahid.” A cartoon knife is superimposed near the Santa hat.

Pro-Isis propaganda posters usually call for lone-wolf attacks in Western urban centers. As Isis struggles to stay relevant following its military defeat in Iraq and Syria, experts say it’s likely these types of threats will increase.

“Terrorist groups, given the uncertainty over their capabilities and desire to instill fear, already have an incentive to misrepresent their strength as greater than it actually is. As they lose territory and therefore resources, this incentive is exacerbated,” Harrison Akins, a researcher at the Howard Baker Center, told Newsweek.