The 20-year-old, who came through the youth system at his current club before making his first-team debut in 2015, made 30 Ligue 1 appearances during the 2016-17 campaign.
Chelsea, Arsenal and Inter Milan have all been linked with the France Under-21 international, but Toulouse have insisted that there has been "no contact" over the highly-rated defender.
"Toulouse football club formally denies any contacts that have been reported in the press over the last few days as regards the players that make up our defence. TFC states that there is no contact and, moreover, we do not expect it either," read a statement on Toulouse's official website.
Diop was part of the France squad that landed the European Under-19 Championship in 2016.