Maradona was hospitalized on Monday for anemia and dehydration.
Early on Tuesday, his personal doctor said his condition had improved.
Later on Tuesday, however, local media reported that Maradona had suffered a brain haemorrhage and had to undergo surgery.
As recently as last Friday, Maradona, widely regarded as one of the best football players of all time, celebrated his 60th birthday.
The Argentine has previously suffered two heart attacks and he has also had liver problems.
Diego Maradona is now the coach of the Argentine Gimnasia y Esgrima.
He met the players at the team's training facility in connection with his 60th birthday last Friday, but is said to have had major problems walking and stayed for only half an hour.
Archive: Maradona hospitalized 3/11 2020
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Legendary Maradona is taken to hospital for depression.
Photo: TT