The reigning Dutch champions announced the dismissal of the former Holland international earlier today following the club's poor start to the Eredivisie season.

AZ have failed to replicate the form enjoyed under Louis van Gaal last season and a 2-1 home defeat against Vitesse Arnhem last night was the final straw for the club's board.

The loss was AZ's seventh in 16 league games this season and leaves them in sixth place, 16 points behind leaders FC Twente and all but out of the title race before Christmas.

AZ also failed to reach the knockout stage of the Champions League under Koeman, while anything less than a win against Standard Liege in midweek will see them fail to gain the consolation of a place in the Europa League.

Koeman, though, claimed he did not expect to lose his job.

"I did not expected this," he said on the club's official website, www.az.nl.

"I am very astonished by the club's communication.

"At no moment did I have the thought or feeling that it would be better if I were to go."

AZ director of football Marcel Brands admitted the decision to dismiss Koeman had not been taken lightly, but insisted the club had to take action to address their poor form.

"It is an odd feeling," he said.

"In my 12-year career as director of football I have never before experienced the dismissal of a coach.

"This was a difficult decision because the relationship between (AZ director) Toon Gerbrands, Koeman and me was good.

"Nevertheless, I am ultimately the one who has responsibility for football affairs.

"The results went against us and the players were not playing at their normal level. Then you must make a decision."

Koeman joined the club in June on a two-year deal as the replacement for Van Gaal, who joined German side Bayern Munich on the back of guiding AZ to their first league title for 28 years.

AZ confirmed Koeman's assistant Tonny Bruins Slot had also left the club, and that control of the first team would pass to the remaining coaching staff.