There is disclosed a panel (10), such as a floor panel, comprising a core (3), an optional upper arrangement (5) and an optional lower arrangement (6). One or more of the core (3), the upper arrangement (5) and the lower arrangement (6) comprises a mineral-based layer (3, 5, 6), preferably comprising magnesium oxide. One or more of the mineral-based layers comprises reinforcement fibres (50) embedded in a mineral-based matrix (51), preferably comprising magnesium oxide. The fibres are configured to increase the tensile strength of the mineral-based layer.