Roma has announced the signing of midfielder Erik Lamela from Argentinian side River Plate.

The 18-year-old leaves the relegated South American giants for a 12million euro fee after weeks of speculation linking him with a move to La Maggica.

A statement on the club's website, asroma.it, said: "AS Roma announces the signing of a contract with Club Atletico River Plate for the acquisition of the player Erik Manuel Lamela.''

The creative midfielder has agreed a five-year contract with the Giallorossi, which faces Slovan Bratislava in the Europa League qualifiers later this month.

Lamela joined River Plate in 2008 and made 31 league starts in the Argentinian top flight last season, as the Buenos Aires club suffered relegation to the second tier for the first time in their 110-year history.

New Roma manager Luis Enrique has already secured the signings of Maarten Stekelenburg, Bojan Krkic, Gabriel Heinze, Jose Angel Valdes and Loic Nego since arriving from Barcelona this summer.