The 20-year-old was with the Bern-based outfit's academy between 2011 and 2018, when he joined the Magpies as a 17-year-old.
And he has now signed a three-year deal with David Wagner's side, who are the current Swiss Super League champions, after leaving United in June.
Touré didn't make a first team appearance during his time on Tyneside, although he did play a handful of games in the EFL Trophy.
He was one of several youngsters to depart St. James' Park this summer. One of them, Lugwig Francillette, has since joined Crawley Town while another, Owen Bailey, has signed for Gateshead.