Chelsea striker Romelu Lukaku may miss Belgium's World Cup opener against Algeria with an ankle problem.
The 21-year-old forward suffered the injury in their 1-0 victory over Tunisia in Brussels on Saturday.
Belgium boss Marc Wilmots was originally positive on the diagnosis, but Lukaku will sit out of training for the next four days and therefore faces a race against time to be fit for their Group H clash with Algeria on June 17.
Wilmots is already without Lukaku's fellow Premier League powerhouse, Christian Benteke of Aston Villa, who was ruled out of the tournament two months ago after damaging his Achilles.
Lukaku has scored six goals in 29 international appearances since debuting in 2010.
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