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The Morocco international tested positive for COVID-19 at the FIFA World Cup, Bayern reported on Saturday (AEDT).

He returned to the team for the Qatar 2022 semi-final against France after missing the last-eight clash with Portugal, but subsequent tests have shown Mazraoui has a mild inflammation of the pericardium, which is the fluid-filled fibrous sac surrounding the heart.

Bayern travelled without him on Friday to a training camp in Doha, and the club has not specified a timeframe for Mazraoui's absence from the squad.

Newspaper Bild has reported the 25-year-old former Ajax player could be out of action for four to six weeks. That would make Mazraoui a doubt for the 15 February (AEDT) first leg of Bayern's UEFA Champions League Round of 16 tie against Paris Saint-Germain.

The Bundesliga leader realeased a statement on its website which read: "Noussair Mazraoui was not able to fly with the Bayern team to Doha on Friday as it prepares for the second half of the season at its training camp.

"The 25-year-old Morocco international tested positive for COVID-19 during the [FIFA] World Cup in December, meaning he missed the quarter-final against Portugal.

"During a follow-up examination in Munich after the [FIFA] World Cup, FC Bayern team doctor Professor Dr Roland Schmidt diagnosed a mild inflammation of the pericardium, which the defender will now cure.

"This means that Mazraoui will not be available to coach Julian Nagelsmann for the time being."

Bayern signed up Dutch defender Daley Blind on Friday (AEDT) to fortify its squad ahead of the resumption of the Bundesliga after its extended winter break.

The 10-in-a-row German champion returns to domestic action against RB Leipzig on 21 January (AEDT).

Midfielder Marcel Sabitzer also missed the beginning of the training camp because of flu, with plans for him to make the trip to Qatar once well.