It is no secret the Rossoneri are looking for ways to reinforce their back line and they have been hot on the trail of the Netherlands international.
Algemeen Dagblad understands that Milan had the player watched at the Under-21 European Championship in Israel.
Martins Indi has a contract until June 2016 at De Kuip, but Feyenoord are, nonetheless, prepared to sell if the right offer comes along.
The defender is desperate to establish himself as a central defender, while he has mostly been played at left-back at De Kuip.
Martins Indi came through the youth ranks at Feyenoord and has already made 76 Eredivisie appearances for the club.
The 21-year-old has also nailed down a regular starting berth in Netherlands national team, and has scored 2 goals in 6 2014 World Cup qualifiers.