Real Madridvs.Man City

A disturbing image threatening the upcoming first legs, purported to be from the Islamic State, was released on Monday by the Al Azaim Foundation, the outlet usually responsible for conveying announcements from the terrorist organisation.

The picture displayed all four stadiums hosting Champions League ties this week - the Emirates, the Bernabeu, the Wanda Metropolitano and the Parc des Princes - along with the message "kill them all" and an image of a gunman.

Tuesday's matches see 14-time winners Real Madrid take on reigning champions Manchester City in the Spanish capital, while Arsenal host Bayern Munich in North London.

Following the conclusion of Tuesday's matches, Atletico Madrid will host Borussia Dortmund, while Paris Saint-Germain host Barcelona in the French capital, where 138 people were killed in attacks by ISIS terrorists in November 2015.

The Champions League threat comes in the wake of another devastating ISIS-claimed attack in Moscow, where 144 people lost their lives at the Crocus City Hall music venue on March 22.

Security for the Champions League ties is expected to be ramped up due to the alleged threat, which UEFA have said that they are aware of, but all four games are set to go ahead as planned.

"UEFA is aware of alleged terrorist threats made towards this week's UEFA Champions League matches and is closely liaising with the authorities at the respective venues," a statement read. "All matches are planned to go ahead as scheduled with appropriate security arrangements in place."

Metropolitan Police Deputy Assistant Commissioner Ade Adelekan has also said that the force are working "closely" with Arsenal's security team to ensure that their clash with Bayern goes ahead "peacefully".