An Italian man who ran onto the pitch during a World Cup match in Qatar carrying a rainbow flag has been released following a brief detention, the Italian foreign ministry said on Tuesday.

The man identified as Mario Ferri also wore a T-shirt with the words "Respect for Iranian Woman" on the back and "Save Ukraine" on the front.

Ferri was on the field for about 30 seconds during the second half of the game between Portugal and Uruguay before being tackled and escorted off by security.

"The foreign ministry, together with the Italian embassy in Doha, followed the case after the pitch invasion," the Italian foreign ministry said in a statement sent to AFP.

"After a brief detention, he (Ferri) was released by the authorities without any further consequences," the ministry said, without specifying where he was held or by whom.

Gay rights and the use of the rainbow flag have been a simmering issue at the World Cup in Qatar, where homosexuality is illegal.

Captains of seven European teams had planned to wear rainbow-themed anti-discrimination armbands during the tournament as part of a campaign for diversity.

But they backed down over the threat of disciplinary action from football's governing body FIFA, including yellow cards.

Ferri has staged similar protests before, including at the 2014 World Cup in Brazil, where he raised the issue of children living in poverty.

On his Instagram account, Ferri posted images from inside the Lusail Stadium in Doha, where Portugal's 2-0 win over Uruguay on Monday took place.

The incident was only briefly shown on television.

"We know what has happened around this World Cup... It's a normal thing to happen," Portugal player Ruben Neves said after the match.

"Of course, we are all with them as well. With Iran as well, with the Iranian women. So I hope it doesn't happen, anything to the boy, because we understand his message, and I think all the world understands it as well."

FIFA maintains rainbow-coloured flags and clothes will be allowed inside stadiums, but some spectators have been ordered to remove items of clothing with the logo during the first phase of matches.