The move, which is initially a loan with view to a permanent deal at the end of the season, comes six months after he became Southampton’s club record signing.
Also on the move was midfielder Hernanes, the Lazio playmaker joining Inter until 2018, while Chelsea’s French forward Gael Kakuta replaced him in the Italian capital on loan until the end of the current campaign.
Across the city Milan completed the loan signing of Adel Taarabt from QPR, and Fiorentina agreed a temporary deal for Sunderland defender Modibo Diakite.
Roma manager Rudi Garcia added two players to his title-chasing squad, although one will not feature for the first team this season.
Rafael Toloi agreed a loan deal with view to a permanent deal from Sao Paulo, while Petar Golubovic signed a four-and-a-half-year contract before being immediately loaned to Serie B side Novara until the end of the season.
Marquinho made his way out of the Stadio Olimpico to sign on loan for Verona, while their rivals Chievo made a double loan swoop for Tiberio Guarente and Victor Obinna from Sevilla and Lokomotiv Moscow respectively.
West Ham completed a loan move for Pablo Armero from Napoli, with Rafael Benitez’s side bringing Faouzi Ghoulam in from Sevilla to replace him.
Parma, unbeaten in 10-games in the Italian top flight, welcomed full-back Cristian Molinaro on loan from Siena, while Nicola Pozzi moved from Sampdoria to Parma and Stefano Okaka went the other way as part of the same deal.
Mid-table Atalanta completed the signing of PSV striker Ruben Bentancourt for an undisclosed fee, while Ukranian Oleksandr Iakovenko moved to Malaga on loan from Fiorentina until the end of the season.
Strugglers Bologna loaned Isuf Cela from Prato, Sassuolo agreed a deal with Napoli for Paolo Cannavaro, initially on loan with view to a permanent deal, and bottom club Catania agreed a deal for Juan Manuel Rios from Montevideo Wanderers in Uruguay.