Here is Riku-Matti Pakkanen’s (Note: “Akkasen” is a typo in the original text, but translates properly) article on how MTK requested an investigation into S-Group (referred to as Ässä) and its market position. The article naturally also discusses Kesko. 
The Central Union of Agricultural Producers and Forest Owners MTK and the Central Union of Swedish-speaking Agricultural Producers in Finland SLC have asked the Finnish Competition and Consumer Authority (FCCA) to investigate the effects of S-Group’s operations on competition.
S-Group’s fiercest competitor, Kesko, is now commenting on the market structure of the grocery trade. Ari Akseli, President of the Grocery Trade Division at Kesko, considers the concentration of Finland’s grocery trade to be a phenomenon typical of the Nordic countries.