BARCELONA (REUTERS) - Barcelona midfielder Ivan Rakitic has agreed a new four-year contract with the Spanish champions until 2021, the club said a day after they reached the Champions League quarter-finals by thrashing Paris Saint-Germain (PSG) 6-1.

The 28-year-old Croatia international has won two La Liga titles, two Copa del Rey trophies and a Champions League crown with Barca since joining from Sevilla in 2014 for an estimated €20 million (S$30 million) and will sign the new deal, which the club said has a release clause of €125 million, on Friday.

Rakitic was left out of the starting line-up in the 4-0 defeat by PSG in the first leg of their Champions League last-16 tie but he played an important role in Wednesday's drubbing of the French champions.

"It's unbelievable, we made the impossible possible," Rakitic said in an interview with CNN on Thursday.

"It's really hard to explain what happened yesterday; I think it was a crazy night, a crazy match and I'm so proud to be part of this team."