(CNN) -- A Catholic website has posted a gruesome video, claiming it shows Syrian rebels beheading a monk.
Catholic Online -- a news and information outlet -- put the video on its website Monday. It shows the slaughtering of three people in northern Syria's Idlib province. The site says one of the three is Father Francois Murad.
Those carrying out the acts "speak Arabic with a broken accent, saying that through this act, they are applying the law of God," Catholic Online says. People in the crowd appear to be taking videos of the executioners.
"It is very important the world knows that Christians are being murdered for their faith, and that martyrdom isn't an ancient phenomenon," Catholic Online said in a report Monday.
"This should make it clear to Christians around the world what jihadists are about. Make no mistake. Catholics and Christians around the globe are under dire threat, particularly from the spread of militant Islam. Until the threat is recognized and taken seriously, martyrdoms like this will continue."
A Vatican spokesman said he was not aware of any video showing the execution of the monk, whose death the Vatican announced last week. The office of the Custodians of the Holy Sepulchre in Jerusalem said to its knowledge there is no such video.
Catholic Online cites local sources linking the militants who killed the monk to Jabhat al-Nusra, an Islamist rebel group regarded as a terrorist entity by the United States.
"The video CLEARLY depicts the beheadings of these victims," Catholic Online said. "DO NOT follow the link unless you are over the age of 18, and are prepared to view content of this nature."
The images renew the daily fears of Christians in the Middle East. They have had a longtime presence in the region and have faced violence, persecution and displacement in recent years.
Christians in Syria have been caught in the crossfire of the country's civil war, in which a government dominated by minority Alawite Muslims is squaring off with a rebellion dominated by Sunni Muslims.
They've also faced hostility in other places, such as Iraq during the war last decade and in Egypt in recent years.
Last week, the Vatican noted the monk's death in a news release, saying it occurred June 23 in Gassanieh -- a predominantly Christian village in the district of Jisr al-Shughur in the province of Idlib, near the border with Turkey.
"The village had been under attack from Islamist rebels for the past few weeks, forcing the majority of the population to flee," the Vatican said, citing the Rev. Pierbattista Pizzaballa, head of all Franciscans in the Holy Land.
"When Fr. Francois tried to oppose resistance to defend the nuns and other people, the guerrillas shot him, killing him," it said.
The violence in Syria since March 2011 has been well-recorded in homemade videos that have surfaced daily. Constant examples of brutality by President Bashar al-Assad's forces have emerged. Over the past year, there also have been a growing number of images showing rebel brutality.
More than 100,000 people have been killed in the conflict, which began as peaceful opposition to the al-Assad regime. As the regime cracked down on the protesters, the conflict morphed into a full-blown civil war.