This paper points out the limitation of existing clustering algorithms based on belief functions that they cannot be applied to complex data (such as mixed data and time series data), and proposes a new algorithm, Soft-ECM, to solve this problem. Soft-ECM requires only a semi-metric to consistently position the center of uncertain clusters, and shows comparable results to existing fuzzy clustering approaches for numeric data. In addition, it shows the advantages of fuzzy clustering that combines the ability to process mixed data and a semi-metric such as DTW for time series data.