The La Liga side have announced the 21-year-old will stay at the club until 2017, with his buy-out clause rising to €45 million
Athletic confirmed the 21-year-old Spain international – whose previous deal expired in June 2015 – has added a further two years to his current terms, with his buy-out clause rising from €37.5 million to €45 million.
The club wrote on their official website: “Athletic Club and the player Iker Muniain have signed the renewal agreement whereby the player will remain with the Reds and Whites until June 30 2017 and his termination clause will rise from €37.5 million to €45 million.”
Premier League side Manchester City were reportedly eyeing up a big-money move for Muniain earlier this year after contract negotiations between the player and Athletic stalled.
The midfielder - who scored seven goals and made three assists in 35 league appearances for Athletic last term - has come through the ranks at the Basque club and has one Spain cap to this name.