France and Spain will step up security ahead of the Champions League quarter-finals in Madrid and Paris on Tuesday and Wednesday nights, top officials said, as Islamic State threats cast a shadow over Europe's top club soccer tournament.

British police said they were aware of reports of threats and had a robust policing plan in place ahead of Arsenal's match against Bayern Munich in London on Tuesday night.

The threats against some of the world's most-watched soccer matches underline the resurgence of Islamic State after several deadly attacks this year, including in Iran and Moscow. They also point to the complex geopolitical backdrop to the world's biggest single sporting event, the Olympic Games, set to take place in Paris in July and August.

At a media event to discuss Olympic security on Tuesday, French Interior Minister Gerald Darmanin told reporters that police had "considerably strengthened security" for Wednesday's fixture between Paris St Germain (PSG) and Barcelona in Paris.

"We have seen, among other things, a communication from the Islamic State that particularly targets stadiums. It is not new," he added.

Islamic State published a post urging followers to recreate a November 2015 attack on the Stade de France stadium, according to Site Intelligence group, which tracks Islamic militant communications.

"Recreate the glory of the Paris 2015 raid and subdue the Crusaders in masses," said the post, which included an image of PSG's Parc des Princes stadium.

Real Madrid play Manchester City in the Spanish capital on Tuesday night as Arsenal take on Bayern Munich in London. Atletico Madrid then host Borussia Dortmund on Wednesday night at the same time as PSG play Barcelona.

"Of course, it's worrying ... Who in this room isn't worried?" PSG coach Luis Enrique told reporters. "It's something I hope can be controlled, and that they're just threats and that nothing disastrous happens." (Reuters)