Witsel, who joined the Russian side last summer, said that he is happy at Zenit but would not rule out a move if one materialises.
"I am completely focused on Zenit at the moment, but PSG are one of the clubs that leave no player indifferent," Witsel told La Derniere Heure. "It would be hard to turn them down.
"There's not a lot I can say about it, because I don't know much about their interest. Things can move pretty fast in football, though."
The deal Witsel signed last summer was for five years.