The 26-year-old limped off after just 20 minutes of Barcelona's 4-1 win over Real Betis on Sunday, the third time this season that he has been forced off with a muscular problem following hamstring and thigh injuries in his right leg earlier in the campaign.
"The club's medical services confirmed after tests this Monday morning that Leo Messi has a torn hamstring muscle in his left thigh and is expected to miss the next 6 to 8 weeks," Barcelona said in a statement."
The first phase of Messi's recovery will be covered in Barcelona and he will then travel to Buenos Aires," it added.
After Sunday's match Barcelona boss Gerardo Martino said Messi's injury troubles were not related and the absence of the four-time World Player of the Year could never be used as en excuse for the team to not perform.
"We have the best player in the world, but we also have four or five of the next six or seven best players in the world. Therefore, as a coach, the absence of Messi should never be used as an excuse for not winning.
"The injury to Messi doesn't have anything to do with the previous ones because it is in the other leg," he added.
Despite losing Messi with the score still at 0-0, Barca cruised to victory as two goals in two minutes from Neymar and Pedro Rodriguez put them 2-0 up at the break.