Romelu Lukaku has suffered a new hamstring injury less than a week after making his return to action for Inter Milan, the Serie A club said on Monday.
In a statement, Inter said that Belgium striker Lukaku had picked up a "strain in the hamstring of his left thigh", the same muscle which kept him out of action for two months.
Inter added that the 29-year-old would be "reassessed in the next few days", and Italian media report that he is not yet at risk of missing the World Cup.
Lukaku made a stunning comeback on Wednesday when he scored in a 4-0 win over Viktoria Plzen which sent Inter through to the last 16 of the Champions League.
He also featured from the bench in Saturday's 3-0 stroll past Sampdoria as Inter moved up to fifth in Serie A, eight points behind league leaders Napoli.
However his latest injury blow means he will miss Inter's Group C trip to Bayern Munich on Tuesday and is almost certain to be absent for Sunday's clash at fierce rivals Juventus.