Manchester City have signed Argentina forward Julian Alvarez from River Plate.
River president Jorge Brito said the Premier League champions have met a release clause in Alvarez's contract.
The 22-year-old, who is considered one of the most gifted young players in South America, will remain at the Argentine champions on loan until July.
Alvarez has scored 36 goals in 96 appearances for River and won six international caps.
He made his international bow against Chile last summer and was part of the Argentina squad that won the Copa America in July.
"If you look at everything Julian has done, it was always likely his release clause would be met," Brito told Argentine network Fox Sports Premium.
"The hardest thing was to agree on a loan move because Julian is practically irreplaceable in the squad."
Reports in Argentina suggest the deal is worth $26m (£19m), which would make him the most expensive player to leave the Buenos Aires club since Javier Saviola moved to Barcelona in 2001.
River coach Marcelo Gallardo said: "It's a good deal as he gets to stay with us for a little longer and joins a big club, one of the top sides in the world with huge economic power.
"At the moment, City don't need him and we don't have to look for a player of his quality, which would be very difficult."
