Marreh's compatriot Bubacarr Sanneh has also switched to Belgium as he joins 34-time Belgian champions Anderlecht in a four-year deal from Danish champions Midtjylland.
Centre-back Sanneh, 23, only joined Midtjylland in January and scored thrice in 22 appearances, helping them to the league title.
"Delighted to complete the move to Anderlecht and I want to thank the owner Marc Coucke for his efforts in bringing me," Sanneh said on Twitter.
