UEFA are to introduce additional security measures at Euro 2024 fixtures and file criminal complaints against any supporter who invades the pitch after six spectators attempted to take photographs with Cristiano Ronaldo during Portugal's Group F win against Turkey in Dortmund on Saturday.

German referee Felix Zwayer was forced to halt the game, which ended in a 3-0 win for Portugal, on four separate occasions after fans ran onto the pitch and headed for Ronaldo.

Two more supporters attempted to reach the former Manchester United, Juventus and Real Madrid forward following the final whistle, prompting Portugal coach Roberto Martinez to voice concerns over the safety of players if a fan has malevolent intentions rather than simply attempting to take a selfie with those on the pitch.

Borussia Dortmund's Westfalenstadion is scheduled to stage a semifinal later in the tournament and will be the venue of Germany's round-of-16 fixture. The host nation tops Group A, but UEFA has now chosen to intensify security at all venues in an attempt to prevent further incidents of fans running onto the pitch.

"Safety and security in the stadium, on the pitch and at team facilities are the ultimate priority for UEFA, DFB (German Football Association) and Euro 2024," a UEFA spokesperson told ESPN.

"To this end, additional safety measures will be deployed in the stadiums to further meet the requirements of the tournament, and to prevent such incidents. For reasons of security, we cannot comment further on specific measures."

UEFA have also urged the German police to take action if spectators run onto the playing surface and move to ban any supporters that do so from the remainder of the tournament.

The spokesperson said: "As a reminder, any incursion onto the pitch constitutes a breach of the stadium rules and will result in expulsion from the stadium, a ban from all tournament matches and the filing of a formal criminal complaint for trespass."

Portugal secured qualification for the round of 16 as Group F winners by defeating Turkey and are due to play their final group game against Georgia in Gelsenkirchen on Wednesday.

The Euro 2016 winners will then play their round-of-16 fixture against a third-place qualifier in Frankfurt on July 1.