Seagulls boss Chris Hughton sent a scout to watch the World Cup qualifier between Austria and Serbia in Vienna, a game the visitors won 3-2 on their way to qualification which was sealed on Monday night.
Speculation has been rife over who the target was and Mitrovic's name was mentioned in the lead up to the game, but now it appears that the Magpies striker was the player under the microscope.
Hughton is in desperate need of more firepower and Mitrovic now looks to be high on his list of targets ahead of the transfer window re-opening in the new year.
The former Anderlecht star has scored 17 goals for Newcastle but is struggling to fight his way back into the side after picking up a three-game ban at the start of the season.
It has been suggested Newcastle will cash in if they receive a big enough offer and the Seagulls are pondering a bid.