West Ham have confirmed the sacking of manager Slaven Bilic, less than 48 hours after Saturday's 4-1 home defeat to Liverpool.
The result was the Hammers's sixth loss from 11 Premier League games this season and left them in the relegation zone.
Former Manchester United boss David Moyes is tipped to take charge of the team on a short-term deal until the end of the season.
"West Ham United can confirm that Slaven Bilic has today left his position with the club," the east London team said on Monday.
"The chairmen and board of West Ham United would like to place on record their thanks and gratitude to Slaven and his team for their services over the past two-and-a-half years, but believe a change is now necessary in order for the club to move forward positively and in line with their ambition."
West Ham added that an announcement regarding a new manager would take place "in the coming days".
Hammers chairmen David Sullivan and David Gold said they had expected Bilic to do better following the high-profile summer signings of Marko Arnautovic, Javier Hernandez and Joe Hart.
"During the summer, the board invested heavily signing the players Slaven believed would complete the squad he needed to push the club back towards the level we had reached in his first season, and we believe we have the players capable of doing that," they said.
"Sadly, performances and results have not been of the expected standard and, in recent weeks, we have not seen enough indication of the required improvement to give us the encouragement that things would change and we would meet our Premier League aspirations this season."
Moyes has been out of management sinceMay, when he left Sunderland having failed to prevent relegation from the top flight.
The Scot enjoyed a successful 11-year spell in charge of Everton but since then has endured disappointing stints at United, Spanish outfit Real Sociedad and Sunderland.