Southampton have completed a £19.2m (€22m) deal for the Argentinian striker Guido Carrillo.

The struggling Premier League club have been desperate to add to their forwards after a difficult first half to the season under Mauricio Pellegrino. The outlay on Carrillo is the first tranche from Virgil van Dijk’s £75m sale to Liverpool, with further reinforcements anticipated. There is strong interest in the Dutch winger Quincy Promes at Spartak Moscow, who could cost a club-record £30m.

Carrillo, who has signed a contract at St Mary’s until June 2021, has been mostly used as a substitute this season, with only two league starts, but has scored five goals for the Ligue 1 champions. Southampton had initially hoped to buy the 26-year-old for closer to £15m and had an offer rejected this week, but have moved to conclude the deal by striking a compromise with the need for forward recruits clear, with the fee to be paid in two instalments.

Charlie Austin is injured, Shane Long has scored once for Southampton since last February and the Italy international Manolo Gabbiadini has struggled badly after a bright start to his career in England last season.

The 6ft 2in Carrillo worked with Pellegrino at Estudiantes and has spent the past two and a half years in France. He joins a side winless in the top flight since November and in the bottom three despite an encouraging draw with Tottenham Hotspur on Sunday.

Carrillo told the club’s website: “I’m very happy. It’s a great feeling to be a part of this club. Lots of things attracted me. I know Southampton from watching the Premier League from when I was small, I’ve always regarded it as the most important league in the world.

“I obviously know the coaching staff, I’ve worked with them in Argentina and I also spoke with some players who were former team-mates in Argentina, who are now playing in the Premier League. They told me all about the club and gave it a shining reference. Therefore, I had no doubts when I took the decision.”