The Magpies are believed to have identified Tomori as a leading target during the current market.
According to Football Insider, Newcastle have been in touch with Tomori's agents to discuss what would be required to bring the Englishman to the club this summer.
The report claims that Magpies head coach Eddie Howe is determined to sign one central defender ahead of the 2024-25 campaign.
Tomori represented Chelsea between 2016 and 2021 before making the move to AC Milan, and he has represented the Italian outfit on 142 occasions in all competitions.
The defender was again an important player for Milan during the 2023-24 campaign, making 35 appearances in all competitions, scoring four times in the process.
Milan 'make contact with Wieffer agents'
Meanwhile, according to Italian journalist Fabrizio Romano, AC Milan have been in contact with Mats Wieffer's agents to discuss a move to San Siro this summer.
The 24-year-old was in strong form for Feyenoord during the 2023-24 campaign, scoring six goals and registering four assists in 42 appearances in all competitions.
Wieffer's future is currently the subject of much speculation, with Milan said to have identified him as their leading midfield target during the summer window.
Romano claims that Milan have been in touch with Wieffer's representatives, and the Netherlands international is keen to make the move to the Italian giants this summer.
The midfielder has scored nine goals and registered 11 assists in 79 matches for Feyenoord.
Southampton lining up move for Wood?
Elsewhere, Southampton could reportedly reignite their interest in Swansea City defender Nathan Wood during this summer's transfer window.
The 22-year-old has been linked with a host of clubs in recent months, and he is believed to have been the subject of two bids from Southampton last year.
According to BBC Sport, the Saints, who have earned promotion back to the Premier League, could launch another move for his services during the current window.
Commenting on the speculation, Swansea head coach Luke Williams said: "Young players playing a lot of Championship football at a decent level will always attract attention from suitors.
"I can't talk any more than that at the moment but it is fair to say that some players have attracted interest."
Wood made 26 Championship appearances for Swansea last season, and he is close to entering the final 12 months of his contract with the Welsh outfit.