Supplemental Info:

The call was issued by Al-Azaim, an unofficial mouthpiece often used by the Islamic State to propagate messages to followers.

Quarter-final first legs: 9/10 April 2024

Quarter-final second legs: 16/17 April 2024

Venues:

• Emirates Stadium, London

• Parc de Prince, Paris

• Metropolitano Arena, Madrid

• Santiago Bernabeu, Madrid

The UK threat threat level remains at "substantial," indicating "an attack is highly likely."

France's nationwide threat level (Vigipirate) is at it's highest level: "Attack Emergency"

Spain's nationwide threat level stands at 4 of 5.

France's interior ministry reports an increased police presence will be in place in Paris in response to the threat. Spain's interior ministry reports more than 2,000 extra security personnel will be deployed. London's Metropolitan Police report security is proportionate to the current UK threat level.