During the 3-0 victory in Dortmund, five individuals managed to get onto the field to snap photos with Portugal captain Cristiano Ronaldo.
Security personnel at Westfalenstadion had to chase down each intruder, causing frustration among players and spectators alike.
“It is a concern. Today, the fans had good intentions. We all appreciate a fan who acknowledges the big stars and icons,” Martinez commented.
“But you have to understand it can be problematic if their intentions are not good. We need to be cautious. This shouldn’t happen – there’s plenty of security.
“We should also send a message to the fans that this is not acceptable. It could lead to more serious issues in the future. It’s not safe for players to be so exposed on the pitch.”
The first fan to invade the pitch was a young boy, whom Ronaldo hugged and smiled for a photo with.
However, Ronaldo became irritated when the third individual attempted to do the same while Portugal was setting up to defend a corner in the second half. Security guards had to restrain this fan near the goal.
At the end of the match, Ronaldo pushed away a fifth intruder and was escorted off the field by security personnel.
Nonetheless, Portugal teammate Bernardo Silva expressed that he was “personally not really concerned” about the pitch invasions.
“It’s just a bit annoying to always have to stop the game because a fan enters the pitch,” Silva said.
“I think that’s the price you pay for being so recognized in the football world and having a player like [Ronaldo] on the team. But in terms of feeling in danger, no, I don’t feel that personally.”
Ian Dennis, BBC Radio 5 Live’s senior football reporter, noted during commentary that “questions will be asked of the security.”
“The security here has been lacking, and this stadium will host a semi-final – they’re going to have to tighten it up,” he added.
UEFA’s disciplinary body will review reports from officials before deciding on any further action.