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We analytically compare the performance of imperfectly symbol- and bit-interleaved block codes over GF(2m) on a first-order Markovian channel in terms of the error probability of a received word. The analytical method developed in Sakakibara (2000) is extended, so that binary transmission of block codes over GF(2m) can be incorporated with the assumption of negligible probabilities of decoding error. Expressions are derived for two decoding strategies; independent bounded-distance (IBD) decoding and error-forecasting (EF) decoding. In the IBD decoding, channel errors up to half of the minimum distance can be decoded in each received word. On the other hand, combining an erasures-and-errors decoding algorithm, more errors may be corrected in the EF decoding. The derived expressions are examined on two typical classes of two-state Markovian channels. Numerical results indicate that a combination of symbol-interleaving and the EF decoding offers the best performance even for imperfect interleaving. This can compensate for the superiority of perfect symbol-interleaving to perfect bit-interleaving addressed by Wicker (1992). It is also found that the optimum depths of symbol- and bit-interleaver is approximately given by 2b and 4b, respectively, where b is the average length of burst errors in bits.