VVV Venlo general manager Hans Soentjens says he is waiting to see if Celtic make an offer for Japan international Maya Yoshida before the transfer window closes.
Yoshida impressed for Japan during the Olympic football tournament and was a target for Aston Villa earlier in the summer before the Premier League club signed Ron Vlaar.
Southampton have also been linked with a bid for the 23-year-old, but Celtic are reported to have watched Yoshida in Saturday's 4-2 defeat by ADO Den Haag.
A £2million fee has been mooted for Yoshida and Soentjens claims SPL champions Celtic have registered their interest in the defender.
"Celtic have officially contacted us to make their serious interest known," Soentjens is quoted in the Sunday Mirror. "We are now waiting for their offer."
Before the weekend, Celtic boss Neil Lennon confirmed he was impressed by Yoshida at the Olympics, but played down reports of an imminent bid for him and compatriot Yuki Otsu, the Borussia Monchengladbach midfielder.
Lennon said: "He (Otsu) is a player we like but we will probably not do anything this window and we will keep tabs on him for now.
"I am aware of Yoshida, I watched him play for Japan against Spain, and I liked the look of him but with regards us being interested or making an offer it is pure speculation at the minute."