Atletico Madrid striker Diego Costa
Chelsea have triggered the release clause in Costa's contractReuters

Chelsea have announced that they have finally reached an agreement with Atletico Madrid over the transfer of striker Diego Costa for a fee believed to be in the region of £32m.

Despite Atletico Madrid President Enrique Cerezo earlier claiming that the deal was far from complete, the Blues have confirmed that they have triggered the buy-out clause in the 25-year-old striker's contract.

"Chelsea Football Club can confirm an agreement has been reached with Atlético Madrid for the transfer of Diego Costa, with Chelsea meeting the buy-out clause for the Spanish international," read a statement on the club's official website.

The Brazil born striker, who has enjoyed a very successful season with Atletico Madrid, scoring 27 goals from 35 appearances in the La Liga, had been strongly linked with a move to Stamford Bridge throughout the season.

Meanwhile Chelsea have confirmed that Australian goalkeeper Mark Schwarzer has penned a new one-year contract extension at Stamford Bridge.

The 41-year-old goalkeeper, who arrived from Fulham to Chelsea on a free transfer last summer, impressed in the Premier League and the Champions League after the Blues' first choice shotstopper Petr Cech sustained an injury towards the end of last season.

Due to this reason, the Blues seem to have decided to let him continue for another year despite there being reports of Thibaut Courtois returning to Chelsea next season.

"Chelsea Football Club is pleased to announce Mark Schwarzer has today (Tuesday) signed a new one-year contract," read a statement in the club's official website.

Elsewhere, the Blues paid tribute to Ashley Cole, who has left Stamford Bridge after eight seasons, following the expiration of his contract.

"Chelsea Football Club today says goodbye to Ashley Cole, a player who contributed enormously to the highly successfully period in our history in which we were crowned champions of Europe and won the League and Cup double for the first time," read an announcement in the club's official website.

The former Arsenal man, who also announced his retirement from international football after being left out of England's 2014 World Cup squad by manager Roy Hodgson, is expected to join Real Madrid for a two-year deal worth £10million