Allan Johnston has been relieved of his duties as Kilmarnock manager with immediate effect, BBC Scotland has learned.
The 41-year-old announced on Thursday he would leave at the end of the season and indicated the sale of Robbie Muirhead was a factor in his decision.
The 19-year-old forward was sold to Dundee United shortly before the closure of the winter transfer window.
Assistant Gary Locke will take charge for Saturday's game at Hamilton.
A statement from the club read: "The board of directors would like to express its thanks to Allan Johnston for his diligent service over the last eighteen months.
"Allan kept the club in the Premiership last season by recording crucial end of season victories and an excellent start to the current league season raised expectations.
"Unfortunately, a number of injuries to key players and a series of poor results followed and although the club sits in eighth place in the Premiership, Allan decided to announce his decision to leave the club to the media on Thursday.
"Allan will stand down as manager with immediate effect and the board has therefore appointed assistant manager Gary Locke as interim manager pending a permanent appointment.
"Alan Robertson will provide support as Gary's assistant.
"Applications for the post of manager are invited and will be considered by the Board over the coming weeks."
Kilmarnock's directors have acted quickly to remove manager Johnston despite chairman Michael Johnston being out of the country.
Although the former Queen of the South boss insisted he would give his full commitment until the summer, the board believe it's best the manager steps aside now.
Former Hearts manager Locke, 39, was appointed as assistant at Rugby Park last summer, shortly after his departure from Tynecastle.
A former Kilmarnock player, Locke will aim to get the team into the Premiership's top six from their current position of eighth.