Struggling La Liga champion Atletico Madrid reported five COVID-19 cases, including coach Diego Simeone, while three Barcelona players also tested positive on Thursday.
Atleti said Simeone, captain Koke, midfielder Hector Herrera plus forwards Antoine Griezmann and Joao Felix all tested positive for the coronavirus.
"All of them are asymptomatic and isolating at their respective homes, in strict compliance with the health authorities' guidelines," Atletico said in a statement.
Atleti, fifth in La Liga on 29 points after 18 games, host Rayo Vallecano on Sunday.
Barcelona, in the meantime, said midfielder Philippe Coutinho, defender Sergino Dest and winger Ez Abde were the latest players to return positive tests.
The Catalans had already been hit by a number of COVID-19 cases in their squad, with Ousmane Dembele, Samuel Umtiti and Gavi set to miss Sunday's La Liga trip to Real Mallorca after testing positive.
Clement Lenglet, Dani Alves, Jordi Alba and Alejandro Balde also returned positive tests this week.
"Footballers Sergino Dest, Coutinho and Ez Abde have tested positive for COVID-19. The players are in good health and self-isolating at home. The club has reported the cases to the relevant authorities," Barcelona said in a statement.
Barca, who last played in the league in a 1-1 draw at Sevilla on Dec. 21, is seventh on 28 points from 18 games.
Real Madrid is also dealing with a COVID-19 outbreak in its squad with Thibaut Courtois, Federico Valverde, Eduardo Camavinga, Vinicius Jr returning positive tests Wednesday.
Luka Modric, Rodrygo, Marco Asensio, Gareth Bale, Marcelo, Andriy Lunin, Isco and David Alaba also tested positive earlier this month.
