Thomson (left) has been stripped of the Hibernian captaincy

"I'm very happy but not surprised," he told BBC Radio Scotland, without revealing details of the offer.

"We have been saying for a number of months now that the players are not for sale.

"So when the transfer window closes in a few days' time hopefully we can get back to talking about football."

The players' agent Willie McKay told the Scottish Daily Mail: "Celtic upped their previous offer, going up to �4.25 - but Hibs knocked it back.

"I believe it is a great offer, as Celtic were willing to wait until the end of the season to get them."

The Edinburgh club previously turned down a �3m joint bid from Premiership strugglers Charlton Athletic.

Thomson has been stripped of the club captaincy, while Brown's recent transfer request was dismissed as Hibs insist the midfielders are going nowhere in this transfer window.

Both players signed long-term deals last March, but McKay has been actively promoting a possible sale through the media.

"Kevin and Scott are a bit upset. At a time when Celtic can go into the loan market and get full internationals through just paying their wages, I think they will just walk away from this," added McKay.

Brown, 21, is currently under contract until 2009, and Thomson, 23, is tied up until 2010.