A farcial Portuguese league match has taken a serious turn after it emerged the omicron coronavirus variant was responsible for Belenenses SAD being unable to field a full XI against Benfica on Saturday.

The smaller Lisbon club took the field with nine men, two of whom were goalkeepers, due to having several members of the squad self-isolating. The match was suspended soon after half-time with Benfica leading 7-0, after injuries meant Belenenses went down to six men, fewer than is the minimum required for a match to continue.

Portuguese health authorities revealed on Monday they had identified 13 cases of omicron, the new coronavirus variant spreading fast globally, among players and staff at the club.

Defender Thibang Cafu Phete tested positive for COVID-19 after returning from international duty in South Africa - where the omicron variant was first identified - on November 17, but is thought to be the only one of the 13 to have been in the country.

This suggested it was one of the first reported cases of local transmission of the virus outside of southern Africa.

A club spokesman said most of those infected were asymptomatic or had mild symptoms, and that 44 players and staff were self-isolating and waiting to repeat tests. Health authority DGS said nearly all Belenenses players had been vaccinated against COVID-19.

The Benfica and Belenenses presidents said that, had they not played the match, they risked being penalised for an "unjustified absence". They blamed the league and DGS for not postponing the game.

The league, which earlier said it did not receive a formal request to postpone the match, was on Monday investigating if the match had complied with health rules.

DGS said it was not up to the health authority to postpone the game.

Benfica said that its players were tested on Monday as they normally are every week and that results were expected later in the day.

Belenenses played against third-division club Caldas on November 21. A Caldas spokesman said they would test their players.

Phete played for South Africa in World Cup qualifiers against Zimbabwe on November 11 in Johannesburg and away to Ghana three days later.