Militants have targeted secularist writers in Bangladesh in recent years as the government has cracked down on Islamist groups seeking to turn the South Asian nation of 160 million people into a sharia-based state.

"Another man whom we believe was one of the main prime suspects in killing the publisher was arrested on Saturday," Monirul Islam, chief of the counterterroism cell of the Dhaka police, told reporters.

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The victim, Faysal Arefin Dipon, had published books written by Avijit Roy, a U.S. citizen of Bangladeshi origin. Roy was also hacked to death by Islamist militants last year.

On July 1, militants killed 20 hostages, most of them foreigners, in an assault on a cafe in an upmarket area of the capital.