Barcelona forward Lionel Messi will be sidelined for around six weeks after tearing a muscle in his left thigh, the club said yesterday.

The Argentine international will miss both legs of his side's Champions League quarter-final tie at the start of April, up to seven Primera Liga matches and the return leg of the King's Cup semi-final against Valencia.

Messi sustained the injury just before halftime of his side's 1-0 Champions League win over Celtic at the Nou Camp on Tuesday.

It is the fourth time in the last three years that the 20-year-old has suffered a similar injury and he was sidelined for five weeks earlier this season with the same problem.

Barcelona's medical services said the player had been following a special training programme since the start of the present campaign.

"The data obtained from the different controls that the player has undergone has determined his availability for each match," they said on the club's website ( www.fcbarcelona.com ).

"But as with any injury there are certain unpredictable factors that are difficult to ward against."

The injury to Messi has caused consternation among his team-mates and the media, who see his absence as a blow to the club's chances of winning any silverware this season.