Dries Mertens could leave Napoli due to a family situation, according to club president Aurelio De Laurentiis.

Manchester United and Tottenham are among the clubs reported to be monitoring Mertens' situation with a view to making an offer for the in-form attacker at the end of the season.

Mertens has plundered 21 goals for Napoli in Serie A this season, thriving in a central role following the sale of Gonzalo Higuain to Juventus for an Italian transfer record, but his four-year spell at the club may be coming to an end.

Reports have claimed Mertens' family are not settled in Naples and De Laurentiis suggested the 29-year-old would be allowed to leave should Napoli receive a high enough offer, with centre-back Kalidou Koulibaly also potentially on his way out.

"Mertens has a family situation that you all know, he has not clarified [his future] 100 per cent, and we are waiting to see what happens," De Laurentiis said on Saturday at a press conference to announce Lorenzo Insigne's contract renewal. 

"Funnily enough, the calls he's getting are due to all the goals he scored thanks to Maurizio Sarri. With a different coach or team-mates, he probably wouldn't score so many.

"This is why I say that in football you need immense humility. There's nothing guaranteed. People ask me what happens if Chelsea make another offer for Kalidou Koulibaly? Our defence would be no weaker without him, because there are alternatives. We leave nothing to chance.

"I don't want anyone to leave and so will try to keep hold of them, but if they want to leave or some crazy person comes along offering to pay the release clause, then we'll get over it, just as we did in the past."

Mertens - whose contract is set to expire in 2018 - rejected the chance to move to the Chinese Super League in the January transfer window and De Laurentiis suggested Napoli will not stand in the Belgian forward's way should he wish to depart.

"You have to love the city of Naples, or you can leave," De Laurentiis said. "Naples is not like living in Turin or Manchester.

"The history of the city continues to develop, year after year, century after century, with millions of stories that can wrap you up in them if you let it happen. To people who say: 'Oh I could never live in Naples' - then go. Who wants you here? Who asked you?"