It is understood that Tottenham Hotspur have had a bid rejected in the region of £15m for the Netherlands international, while Arsenal have also been credited with a summer move.
Janssen has claimed that he is 'frustrated' with a lack of movement this summer and wants his future to be decided before returning to pre-season training.
"I have expressed my choice at the club. Tottenham Hotspur have made a high bid in my eyes. There has been an offer around €18m (£14.9m), but AZ will not even come to the table," Janssen told reporters. "I would like somewhere else as soon as possible to start my preparation. This is frustrating."
The 22-year-old scored 31 goals in all competitions for AZ during the 2015-16 campaign.