Belgian holding company Groupe Bruxelles Lambert (GBL) has taken a stake of nearly 3 percent in German fashion group Hugo Boss, monthly Manager Magazin reported, citing unidentified sources.

Shares in German fashion house Hugo Boss jumped more than 8 percent on Thursday after a report that the holding company of Belgium's richest man, Albert Frere, has taken a stake of nearly 3 percent and wants to increase it further.

Frere's Groupe Bruxelles Lambert declined to comment on the report in Germany's Manager Magazin, which cited unidentified company insiders. A Boss spokeswoman said no regulatory filing had been made, declining further comment.

Frere has a reputation for helping to shake up the companies in which he invests.

After he and other activist investors took stakes in Adidas in 2015, the German company appointed a new chief executive and announced plans to sell its golf business. Shares in Adidas, in which GBL still has a 5 percent stake and a representative on the supervisory board, have more than doubled since Frere invested.

Hugo Boss shares initially jumped more than 8 percent before retreating slightly. The shares were up 6.2 percent up at 63.98 euros at 1320 GMT, their highest in a year and the biggest gainer on the STOXX 600 .

Manager Magazin said that GBL has a good relationship with Boss's biggest shareholder, Italy's Marzotto family, which owns a 10 percent stake. The publicaion noted that GBL and Marzotto this month sold Italian sneaker maker Golden Goose to private equity firm Carlyle.

Hugo Boss promoted finance chief Mark Langer to chief executive last year after the departure of Claus-Dietrich Lahrs following a series of profit warnings.

Langer has announced plans to try to revive the struggling company by cutting brands, closing stores and putting the focus back on its core menswear business.