Arsenal's new 32.5 million ($36m) signing Mikel Merino will be out for several weeks after suffering a fractured shoulder in his first training session, manager Mikel Arteta confirmed on Friday.

The 28-year-old midfielder sustained the injury when colliding with centre-back Gabriel Magalhães during practice at London Colney.

Merino, who joined Arsenal from Real Sociedad, was hopeful of making his debut against Brighton in Saturday's Premier League clash at Emirates Stadium but is now set for a spell on the sidelines.

"Very unfortunate," Arteta told a news conference. "Yesterday [Thursday] he had a collision and he has a shoulder injury unfortunately. It looks like he's going to be out for a few weeks. First session. He was really excited and everything was looking really good.

"He landed on the floor and Gabi landed on top of him and it looks like he has a small fracture, probably.

"We have to see [how long he is out for]. He was in so much pain. We'll have to do some more tests on that and then we'll have more conclusive answers."

There was better news regarding forward Gabriel Jesus, who underwent an MRI scan on a groin injury amid fears he could be ruled out for a lengthy period.

However, while Arteta ruled out the Brazil international against Brighton, he added: "He is progressing really well. He had a little muscle injury and he is doing quite a lot of stuff already, so we expect him to be with us pretty soon."