Victor Boniface, Victor Osimhen and Omar Marmoush are all on United's radar, says Sky Sports.
They belong to Bayer Leverkusen, Napoli and Eintracht Frankfurt respectively.
Osimhem is currently on loan to Galatasaray and has a buyout clause in his contract with Napoli set at €75m.
Frankfurt is asking between €50-60m for Marmoush - who has already been strongly linked with Liverpool .
Nigeria international Boniface is also being discussed inside United. He has a contract at Bayer to 2028.