The Serbia international scored nine times in 34 games last season for Newcastle, but couldn't prevent the Magpies being relegated to the Championship.
Mitrovic has found first team football at St James' Park hard to come by this season, with Dwight Gayle impressing in the central striker role, having scored 17 goals in 18 games for Newcastle.
Mitrovic would most probably cost around £15m, a price that relegation threatened Crystal Palace and Swansea would likely pay, while at the same time for Newcastle, it would make financial sense for a player who is not playing regular first team football.
The 22-year-old is thought to be keen to play regular football and in the top-flight, meaning that he may well end up in south London or south Wales in the new year.