Liverpool did not reveal details of the deal, but reports suggest Coutinho has signed a five-year contract worth between £150,000 ($188,800, 175,650 euros) and £200,000 per week.
Coutinho, 24, joined Liverpool from Inter Milan in a £8.5 million move in January 2013 and has since become the team’s attacking fulcrum, scoring 34 goals in 163 appearances.
“Ever since my arrival here, I was welcomed with open arms by the supporters and everyone at this football club,” Coutinho said in comments published on the Liverpool website.
“This is an important factor that carries weight when you decide to remain here for a longer period and this did have a lot of weight when I thought about the renewal of my contract.
“I can only thank every supporter for their faith in me. I really hope to repay them. I will do my very best on the pitch to create assists for my team-mates and score goals for us to try and win trophies and titles.”
An artful attacking midfielder and set-piece specialist with an eye for the spectacular, Coutinho has been capped 23 times by Brazil, scoring six goals.
He has been in sparkling form this season, scoring six goals in 18 games, and was badly missed by Liverpool after sustaining an ankle ligament injury in November that kept him out for seven weeks.
Liverpool manager Jurgen Klopp said Coutinho’s new contract, which is not thought to include a release clause, represented a “big statement”.
“He is truly world-class — in that very top bracket,” Klopp said.
“The fact he wants to stay here and be part of what we are looking to build and develop shows his personal commitment is to make himself better and be an integral part of something that is very special.
“We have total belief in our project, but when a player of Phil’s calibre and status commits for this length of time it shows that our faith is shared throughout the game.
“He knows he can fulfil his dreams and ambitions here at Liverpool. This is a big statement. I look forward to seeing Phil create many more great memories and moments for this club.”
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