European football's governing body, UEFA, has said it is aware of a terror threat made regarding this week's Champions League quarterfinal ties, but it said the matches will still go ahead as planned.
The Al-Azaim Foundation -- a media arm of ISIS-K -- issued multiple social media posts calling for attacks at stadiums hosting Champions League quarterfinal matches.
On Tuesday, Arsenal host Bayern Munich at the Emirates Stadium in London and Real Madrid play Manchester City at the Bernabéu stadium in Madrid, while on Wednesday, Paris Saint-Germain face Barcelona in Parc des Princes in Paris and Atlético Madrid host Borussia Dortmund at Madrid's Wanda Metropolitano Stadium.
France's interior ministry has confirmed an increased police presence will be in place in Paris on Wednesday in response to the threat, while Spain's interior ministry said there will be more than 2,000 extra security personnel in line with typical operations for a major football fixture.
"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," the governing body said in a statement to ESPN. "All matches are planned to go ahead as scheduled with appropriate security arrangements in place."
London's Metropolitan Police told ESPN in a statement that the nationwide threat level remains at "substantial," but acknowledged the terror threat against the Champions League ties.
"We're aware of online and media reports in relation to calls to target matches across Europe and here in London," said Deputy Assistant Commissioner Ade Adelekan, who is overseeing policing in London on Tuesday.
"However, I want to reassure the public that we have a robust policing plan in place for tonight's match and we continue to work closely alongside the club's security team to ensure that the match passes peacefully.
"As ever, we ask the public to remain vigilant, and if they see any that doesn't look or feel right, then report it to police or security staff."
An Arsenal spokesperson told ESPN the club is working closely with the Metropolitan Police, adding: "Our planning for tonight's fixture is no different and our approach, working together with the Police and UEFA, is proportionate to the current UK threat level."
Spain's interior ministry told ESPN in a statement: "The State Security agencies have designed an operational deployment in which more than 2,000 National Police and Civil Guard agents will participate, to which members of Madrid's Municipal Police will be added, to ensure the correct development of the two sporting events taking place today [Tuesday] and tomorrow [Wednesday] in the capital.
"This deployment is coordinated and has the support provided for in the measures that, throughout the territory of the State, establishes the Anti-Terrorist Prevention, Protection and Response Plan for the current level 4 out of 5 of anti-terrorist alert, to which various measures have also been added to prevent these type of contingencies."
Meanwhile, French media reported that the country's Interior Minister Gérald Darmanin said he is aware of the threat from Islamic State and has organised increased security measures.
"We have seen, amongst others, a message from the Islamic State which particularly targets stadiums, which isn't new," Darmanin told reporters on Tuesday. "The police chief, with whom I spoke very early this morning, has considerably reinforced security resources."
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The return matches in the Champions League are scheduled for next week.
PSG defender Danilo said he and his teammates "need to concentrate on the soccer," but manager Luis Enrique said the threat was worrying.
"Who wouldn't be concerned by that. Of course we're concerned," Luis Enrique said. "We hope it's only a threat and that nothing will happen."
Information from ESPN's Alex Kirkland, James Olley and the Associated Press contributed to this report.