French midfielder Mathieu Flamini has returned to Arsenal after being released by AC Milan, the Premier League club announced on Thursday.
The 29-year-old central midfielder made 153 appearances for Arsenal between 2004 and 2008 before leaving for Milan, where he spent five seasons.
He has been training with the Arsenal squad for the past month and Arsenal manager Arsene Wenger said he was delighted to have Flamini back on board.
"We are very pleased Mathieu has agreed to rejoin us," Wenger told the Arsenal website, www.arsenal.com.
"He is a player of real quality, with a fantastic work rate and great mentality.
"As we know, Mathieu is a strong midfielder, but is also comfortable playing in defence too. He is a very good addition to our squad."
Flamini's return comes at an opportune moment, with Wenger currently deprived of midfielders Abou Diaby, Mikel Arteta and Alex Oxlade-Chamberlain due to injury.
Wenger also revealed on Thursday that the club will be without Lukas Podolski for up to 10 weeks after the German forward damaged his hamstring in Tuesday's 2-0 win over Fenerbahce.
"It is bad news about Lukas Podolski as he will be out for eight to 10 weeks," Wenger told the Arsenal website.
"His hamstring is much more damaged than we thought at the start. It is very disappointing and we have paid a very heavy price for that win. We have to be patient now."
Podolski expressed his disappointment on Twitter, writing: "As you surely know, my injury is worse than we had expected. I'm sad but I'll do everything to come back soon. Thanks for your wishes."
Midfielder Aaron Ramsey scored both goals against Fenerbahce but came off in injury time with a groin problem, while Jack Wilshere was the recipient of some robust challenges in the game's final stages.
However, Wenger said that both players should be available for Sunday's north London derby against Tottenham Hotspur.
"The news is quite positive," he said. "They just had bumps and bruises. They will be involved."
Wenger revealed that Arteta and captain Thomas Vermaelen are still weeks away from full fitness.
"Arteta is doing OK, but there are a few weeks to go with him," he said. "Thomas Vermaelen could be back after the international break."
Given Arsenal's injury problems, Flamini could go straight into the squad for Sunday's meeting with Spurs.
Former Auxerre striker Yana Sanogo is the only other player to have arrived at the Emirates Stadium during the close season, but Wenger says he remains in the hunt for new players.
"When you think that we lost three players of the stature of Arteta, Oxlade-Chamberlain and Podolski for three months basically before the season really starts, it's very hard to take," he said.
"We are in a position where you want some more players."