The Sun revealed that United scouts were among the spectators during the Foxes 2-1 defeat to Liverpool prior to the international break and they were impressed with the player’s display.
The Gunners are also said to be eyeing a move for the fullback as part of Unai Emery’s plans to upgrade his fragile defensive unit in January.
Chelsea are also in the race for the player as they hope he will be available next summer.
As it stands, Manchester United are leading the two London clubs and they are reportedly set to cough out £50m in next year.
Meanwhile, the Red Devils have stepped up their plans to lure James Maddison to Old Trafford as they are set to launch a huge £80m bid for his services.
The Englishman has been a major source of transfer speculations in recent weeks as his future at the King Power Stadium remains uncertain.
Having signed Maguire from the Foxes in the summer, the Red Devils will hope to explore the imitate relationship between both clubs in their favor.