A method for the spinning of a fiber comprising cellulose nano-fibrils being aligned along the main axis of the fiber from a lyotropic suspension of cellulose nano-fibrils, said nano-fibril alignment being achieved through extension of the extruded fiber from a die, spinneret or needle, wherein said fiber is dried under extension and the aligned nano-fibrils aggregate to form a continuous structure. The fibrils used in this method can be extracted from a cellulose-rich material such as wood. The invention also related to a cellulose-based fiber obtained according to this method and to a cellulose fiber which contains at least 90% wt of crystallized cellulose.