Despite the Belgian first division being cut short by the coronavirus pandemic the Brussels club elected to go back to work "for those players who want to".
Among those to question Anderlecht's decision was virologist Marc Van Ranst who described it as "legal but a bad signal" during lockdown.
Another doctor wrote to the Brussels mayor telling him: "It's incredible. (It) goes totally against government recommendations and the advice of experts."
Police are carrying out daily checks to ensure the players are respecting the strict health measures put in place to stop the spread of COVID-19 which has claimed 4,400 lives in Belgium.
Anderlecht, placed eighth in the league, say each player is designated a zone on the pitch and his own ball, no passing is permitted. AFP PDSPDS