The International Press Institute (IPI) today called for a thorough and swift investigation into yesterday’s brutal murder of American-Bangladeshi blogger Avijit Roy in Dhaka.

Roy and his wife, Rafida Ahmed, were leaving a book fair in the Bangladeshi capital late in the evening when they were attacked by unidentified men with machetes.

Roy died of his injuries shortly after he arrived at a hospital. His wife also sustained serious injuries and remains hospitalised.

According to a local police commissioner, the militant group Ansar Bangla 7 claimed responsibility for the attack. The group reportedly posted a number of messages related to the crime on Twitter following the crime, with one stating that Roy “was a target because of his crime against Islam”.

The attack is one of an increasing number on secular writers in the country. Roy was the founder of the blog “Mukto-Mona” (Free-Mind), which criticised religious intolerance and extremism.

IPI Director of Advocacy and Communication Steven M. Ellis condemned the attack and called on officials to bring the perpetrators to justice.

“While violence is never an acceptable response to criticism or perceived insults, this attack is particularly horrific and cannot help but have a chilling effect, which we fear was precisely the attackers’ intention,” he said. “Bangladeshi authorities have a responsibility to protect against such brazen attacks on free expression, and we urge them to take all steps to bring those behind this attack to justice, and to do so in a swift and transparent manner.”

Roy’s family said he had received a series of threatening emails and social media messages for his writings. One of the online retailers of Roy’s books, rakamari.com, also reported receiving threats for selling his works.

Earlier today, demonstrators gathered at the site of the murder to protest Roy’s death, demanding that authorities apprehend the attackers.