"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," officials said in a statement. "All matches are planned to go ahead as scheduled with appropriate security arrangements in place."

Meanwhile in Madrid, authorities there have opted to keep the roof of the Santiago Bernabeu Stadium closed as a precaution.

The other two matches are scheduled for Wednesday night, with Paris Saint-Germain taking on Barcelona in the French capital and Borrusia Dortmund traveling to Spain to play Atletico Madrid at the Metropolitano Stadium.