Barcelona striker Robert Lewandowski suffered an ankle sprain in their Champions League clash at Porto and will be out of action with no timeline for his return, the club said on Thursday.

Polish international Lewandowski, 35, was on the receiving end of a crunching tackle from Porto's David Carmo in the first half of Barca's 1-0 win on Wednesday.

The injury is a huge blow to the Spanish champions, who are one point behind LaLiga leaders Real Madrid after eight games. Barca host Real in the 'Clasico' later this month.

"Tests conducted this Thursday morning have revealed that Robert Lewandowski has sprained his left ankle and will be out of action until the injury heals," Barca said in a statement.

Lewandowski is the team's top scorer in the league this season with five goals and three assists. Barcelona next play at Granada on Sunday.