Celtic chiefs are reportedly braced for a transfer bidding war to break out for Matt O'Riley after Atletico Madrid tabled a loan-to-buy offer.

The Spanish giants made a formal offer to Celtic to land O'Riley on loan until the end of the season with an obligation to then purchase the player.

The Scottish Sun claims the bid would see Atletico pay a loan fee to Celtic immediately before further payments which could break the £20m barrier to make the transfer permanent.

It's thought Celtic chiefs are ready to boot out the offer from Atletico but could face more big decisions over O'RIley's future in Glasgow with a host of clubs interested.

Previously, Bologna and Leeds had deals knocked back for O'Riley, while Girona have been credited with a serious interest in the January transfer window.

Now, though, it's reported further clubs could test Celtic's transfer resolve with moves for O'Riley after Atletico started the bidding this month.

READ MORE: Celtic must reinvest if Atletico game-changer lands O'Riley

The Daily Mail suggests several English Premier League sides are ready to bid for O'Riley, while interest from Serie A side Inter Milan remains.

Brendan Rodgers previously insisted Celtic don't need to sell the playmaker during the January window.

He said: "The club is in a really strong position and we have no need to sell and no thoughts of selling.

"Naturally it is the time of the season where there is lots of speculation and gossip surrounding players.

"Matt is really, really happy here. He has signed a new deal and he has really progressed. He is into double figures with his goals and his assists are there.

"For him, as a young player, who I know is a brilliant professional, all he wants to do is improve and you can see his improvement here just by taking things day by day and assessing it from there."