Celtic boss Neil Lennon insists striker Gary Hooper is not for sale, amid reports Russian side Zenit St Petersburg are keen.
The former Scunthorpe striker has proved a huge success since his £1.6million move to Celtic Park in 2010.
Hooper already has 16 goals to his name this season and was the subject of a £5million bid from Championship side Southampton in the January transfer window, an offer Celtic instantly rejected.
There is speculation that Zenit will launch a £7million move before the Russian transfer window closes on February 24, but Lennon insists the frontman is not for sale at any price.
He told the Evening Times: "You simply can't put a price on Gary. I saw figures bandied about during the last transfer window. But he's just too valuable to this club even to consider selling him."
Meanwhile, Celtic can move four points clear at the top of the SPL table if they win their game in hand at Hearts on Wednesday.
However, Lennon insists the title race is still wide open and he will not tolerate any complacency within the Celtic camp as he bids to land the league crown.
"Rangers are the champions and they are the champions for a reason," said Lennon. "We have to take on all the challenges that come our way and overcome them as best we can. There will be no room for complacency here and anyone showing that will be not playing."