The 19-year-old has scored once and provided five assists in 23 Serie A appearances this term.
Barcelona are believed to view the teenager as a future replacement for Sergio Busquets, with the Spanish champions potentially moving for the Italy international during this summer's transfer window.
However, according to Tuttosport, City are also interested in the central midfielder and could be ready to rival Barca for his signature ahead of the 2020-21 campaign.
Despite his age, Tonali played a key role in Brescia earning promotion from Serie B last term, scoring three times and providing seven assists in 34 appearances in all competitions.
Manchester United, Juventus and Paris Saint-Germain are also believed to be admirers.