LONDON — Arsenal began its off-season transfer activity early by signing Switzerland midfielder Granit Xhaka on Wednesday, adding another talented player to the most competitive area of the squad.

Amid calls for the club to sign a prolific striker or a dominant centre back, Arsenal manager Arsene Wenger has again chosen to bolster his midfield by signing a player who captained German side Borussia Monchengladbach to fourth place in the Bundesliga this season.

The fee was undisclosed and the 23-year-old Xhaka will join up with his new club on a "long-term contract" after playing at the European Championship with Switzerland.

"We have been watching him for a long time now," Wenger said, "and he is a player who will add quality to our squad."

Xhaka, who has played 41 games for Switzerland, can play as a central midfielder or in the more attacking positions behind the striker. Arsenal already has fierce competition in those areas.

Xhaka has described himself as an "aggressive player and also a leader," characteristics that Arsenal's players have perhaps been lacking since the team's last Premier League title in 2004.

"I'm only 23 but I captained a good team in Germany," Xhaka said.

"It's a fight (in the Premier League)," he added. "I like that but Arsenal can also play football and that's very good."