Online propaganda from a pro-ISIS channel has threatened a Christmas terrorist attack against the Vatican, with a poster inciting 'Christmas blood'.

The incendiary poster comes from the ISIS-affiliated group Wafa Media Foundation, according to the Maryland-based extremist counter-terrorist organisation SITE Intelligence Group.

The poster is headlined 'Christmas blood' followed by the words 'so wait...', over a driver's-seat image of a car heading towards the Vatican's St Peter's Basilica. An assault rifle, rucksack and explosives appear on the passenger's seat, while the rear-view mirror depicts the driver as a black-clad masked jihadi. The driver is led by a satelite navigation system. 

St Peter's is the heart of the Catholic Church and the seat of Pope Francis, who traditionally uses the iconic setting for celebrating Mass at Christmas.

The image is believed to be an incitement to 'lone wolf' agents and vehicular-based attacks, which have become increasingly common in ISIS-claimed terror attacks, particularly in Europe. In 2016 an ISIS-inspired attack saw one truck driver kill 12 people, and injure many more, at a Berlin Christmas market.

The radical Islamist group has significantly diminished in military terms, having recently been driven out from former strongholds in Syria and Iraq. But its propaganda machine remains as an effective route to promote terror and spread fear.

Rita Katz, director of the SITE Intelligence Group, told Newsweek: 'Wafa Media Foundation specialises in these types of graphics. Wafa's threat, like others recently issued by pro-ISIS media groups, is a specific attack directive within a larger push by ISIS for lone wolf attacks as it rapidly loses territory in Iraq and Syria.

'Though these threats should be taken seriously, there is also a publicity element to pro-ISIS media groups' threats against places like the Vatican or events like 2018 FIFA World Cup.'

As a landmark of Western society and the symbolic centre of Christianity, the Vatican is a popular target among Islamists. In August another pro-ISIS group released a video inciting attacks against Pope Francis, showing photographs of the pope being torn into pieces.

The video warned: 'We will have our vengeance, we will arrive in Rome.'