The 27-year-old midfielder has made over 150 appearances for the club, winning the Russian Premier League in 2014-15.
But after a four-year stint in Russia, Witsel says he is keen on a change of scenery, just days after confirming that Roma are among those interested in his services.
"Russia was a nice adventure, but it's time for me to change," said Witsel, who is in France representing Belgium at Euro 2016.
"I don't know whether I'll go to the Premier League or to Serie A.
"Italian football fascinates me and at 27 it would be the right move. [AC] Milan had looked for me, it's true, but that's a story from a long time ago.
"Now the only thing I'm thinking of is Euro 2016. The next step is to beat Sweden."