The 21-year-old has been in sensational form this season for AZ Alkmaar, notching 20 goals in Eredivisie action – the highest single tally in the division – to keep his side in contention for a Europa League qualification slot.
His domestic showings have also seen Janssen thrust into the Oranje set-up, and he netted a penalty kick in his second ever appearance for them against England last week.
And it seems that his performances have alerted Man United and Everton, with reports claiming scouts from both sides were in attendance to watch the striker in action against PSV Eindhoven on Saturday.
The forward was impressive despite the 4-2 home loss, while representatives from Paris Saint-Germain also looked on.
Prior to the PSV defeat, Janssen had netted in seven consecutive league matches for AZ.