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Allan Johnston's side are in a safe position in the Premiership but were knocked out of the Scottish Cup by Rangers in November

Kilmarnock manager Allan Johnston has made a surprise announcement he will leave his post in the summer.

The 41-year-old "just made my mind up before I came in" to a press conference ahead of Saturday's game with Hamilton.

He said the sale of Robbie Muirhead to Dundee United on Monday was a factor behind his decision.

"I never found out Robbie was away until five past 12 [on deadline day]. Stuff like that, it is not the way things are done," he said.

The Ayrshire side sold 18-year-old Muirhead to Scottish Premiership rivals United for £150,000 plus add-ons.

Asked about the departure of the Scotland Under-19 player, Johnston said: "There is a number of things but that certainly doesn't make your job any easier.

"It was really difficult to arrive at the decision [to leave]. It is not something you want to do.

"I trust in the players I have got but I think it is the best decision for myself and the club.

"There is a new chairman coming in and I think it is important that there is a freshness about the club and it is time to move on anyway."

Kilmarnock sit eighth in the Premiership, six points adrift of a top-six place with a game in hand, and 10 clear of the relegation zone.

Johnston added: "It is disappointing but there is still a job to be done between now and the end of the season.

"Until then I will give 110%. It is a good club and it is important we finish the season strongly."

A statement on the Kilmarnock website external-link said the board would "now convene to consider their options".

The former Queen of the South boss - who played for Hearts, Rennes, Sunderland, Rangers and Kilmarnock among others - moved to Rugby Park in 2013 following Kenny Shiels' sacking.