Ronaldo Messi Real Madrid Barcelona
File photo of Cristiano Ronaldo and Lionel Messi.Reuters

Terrorist organisation ISIS has released a digitally-altered poster with which they have threatened to behead Barcelona and Real Madrid superstars Lionel Messi and Cristiano Ronaldo at the upcoming FIFA World Cup in Russia.

The new threat from the notorious outfit comes even as it has been urging "lone attackers" to strike during the tournament, according to The Sun.

ISIS had previously threatened Messi when they released a doctored photograph of Argentina forward behind bars, crying blood along with a caption: "You are fighting a state that does not have failure in its dictionary."

However, this is the first time Portugal and Real forward Ronaldo has been mentioned by the Islamic State in its ever-increasing threats in the lead up to the quadrennial football showpiece in Russia, starting June 14. '

The recently-released poster shows a morphed image of masked terrorists beheading Messi and Ronaldo as the football stars are pinned to the ground at a packed stadium. The poster carries a caption, reading: "Your blood will fill the ground.".

See photo: ISIS poster threatening to behead Messi and Ronaldo at FIFA World Cup 2018 (Warning: Graphic content)

Cyber intelligence firm Sixgill, which monitors ISIS chatter and the dark web, revealed the threat, according to The Mirror. The poster was released by a pro-ISIS group on the cloud-based instant messaging application, Telegram.

This is not the first time ISIS has threatened to carry out terrorist activities at a football tournament. They have previously threatened to disrupt Euro 2016 and Women's Euro 2017, according to the Washington Post.

The latest threat comes days after ISIS supporters threatened a "life or death" match at the World Cup. A poster showed ISIS soldiers, carrying AK-47, lining up for "big match" against the host nation, who are dressing in their traditional red kit.