The 24-year-old will miss Spain's Nations League matches against Denmark on Saturday and Serbia next Tuesday, national team coach Luis de la Fuente confirmed.
Media reports said Ferran could be out for six to eight weeks after he picked up the injury in Barca's 3-0 win at Deportivo Alaves on Sunday where he limped off after five minutes.
"Tests carried out on Ferran Torres confirm that he has an injury to the biceps femoris muscle in his right thigh. His return to training will be dependent on his recovery," the Catalan club said.
Barcelona are navigating an injury crisis, with Dani Olmo, Gavi, Fermin Lopez, Andreas Christensen, Ronald Araujo, and goalkeeper Marc-Andre ter Stegen among the players sidelined.
"Ferran's injury is worrying. We don't have many options in attack," Barca manager Hansi Flick said on Sunday.
He has made 10 appearances for Barcelona this season.
