An alleged racist incident marred a Portuguese league match on Sunday as Porto forward Moussa Marega walked off midway through a match due to abuse from fans.

Marega left his team's 2-1 win at Vitoria Guimaraes in the 69th minute, pointing to the crowd and raising his middle fingers to the stands. Players and staff from both teams tried to console Marega to stay on the field.

The player was also given a yellow card by the referee as he walked toward the tunnel.

Marega, a French-born Mali international who had previously played for Guimaraes on loan in 2016-17, scored Porto's game winner before the incident.

In an Instagram post after the match, Marega said: "I would like to only say to those racist idiots in the stands, go f--- yourselves."

The 28-year-old also criticised the game's referees, saying: "I appreciate the officials for not defending me and for giving me a yellow card for defending the color of my skin. I hope to never find you on the football pitch again. You're an embarrassment!"

The league's organising body Liga Portugal condemned the chants.

"Liga Portugal does not agree and never will with acts of racism, xenophobia or intolerance that jeopardize the dignity of footballers or any human beings," said a statement on the organisation's website.

"Liga Portugal will do everything to ensure that this episode and all other racist incidents do not go unpunished.

"We believe this is a fight where your team's colours do not matter and everyone must come together to eradicate this scourge on the game."

Guimaraes said it would investigate the incident.

"[The club] will not fail to censor any and all manifestations of violence, racism or intolerance,'' it said.

It added that the club "will verify what happened during the game played at Estadio D. Afonso Henriques, acting firmly and consequently, in full cooperation with the competent judicial entities.''

Porto boss Sergio Conceicao called the incident "unfortunate" after the match.

"We are a family regardless of nationality, skin colour, hair colour. We are human, we deserve respect," Conceicao said. "We are completely indignant about what happened. I know the passion that exists for Vitoria and I think most of the fans do not see themselves in the same attitude of some people who have insulted Moussa since the warm-up."

Porto director of communications Francisco Marques added on his own Twitter account: "Marega was fed up and left the pitch and Porto was forced to make a substitution due to racism."

Portuguese newspaper A Bola reported that no Porto players spoke to the media after the game in solidarity with Marega.

Vitoria coach Ivo Vieira said he did not want to comment on the incident as he was not certain what had happened.

"I prefer not to speak about a situation without being aware of all the facts. But if the player was provoked, then he should not have been," he said.

Porto are second in the Portuguese top flight, trailing leaders Benfica by a point after 21 games.

Information from Reuters was used in this report.