Arsenal have confirmed the permanent signings of on-loan defenders Pablo Mari and Cedric Soares, while there have also been extended deals for Dani Ceballos and David Luiz.
On Wednesday, the Gunners confirmed that the club had exercised its option to sign both Mari and Soares permanently following the defensive duo's respective loans from Flamengo and Southampton.
Scroll through the gallery above to see Arsenal's latest transfer business
Arsenal also confirmed that Luiz, whose contract was set to expire at the end of the season, had signed a new one-year extension, and Ceballos, who is loan from Real Madrid, will remain at the club until the end of the current campaign.
"I am really happy that we will have these players in our squad for the future," technical director Edu told the club's official website.
"They have been part of the long-term technical plan Mikel (Arteta) and I have developed. They bring the right balance to our squad.
"David is a really important player for us. He has played most of our matches this season and has been important for the team. His passing, his communication with the team on and off the pitch. He helps everyone.
"With Pablo, we're all disappointed he got injured at Manchester City. Since Mikel arrived here, he was asking for a central defender who was left-footed.
"We were really pleased with Pablo – his behaviour, the way he is training, his mentality and his quality. Unfortunately, he has that injury, but of course, we are really happy to keep him for the future.
"Cedric is also going to be an important player. He has been unlucky with the injuries but he is close to being ready and gives us more strength in the right-back position.
"We're also pleased Dani will finish the season here. He is making a good contribution and we look forward to him having a strong finish to the season."