Two criminal cases have been filed in Bangladesh against three men arrested for hacking to death a Hindu tailor.
The murder of Nikhil Joarder by suspected Islamist militants on Saturday was the latest in a wave of murders over the past three years.
More than 20 people, including bloggers, academics, foreigners and religious minorities, have been killed.
Islamic State said it carried out the attack because the dead man had insulted the Prophet Muhammad.
However the authorities deny the group is active in the country.
The BDNews24 news agency has reported that two cases had been initiated in connection with the murder – one by victim’s family and another by local police over the discovery of small bombs allegedly found in a bag left at the scene of the crime by the assailants.
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Police in the central district of Tangail say that among those they have detained over the murder is the principal of a madrassa or Islamic religious school.
A local official of the country’s largest Islamic party, the Jamaat-e-Islami, is also being questioned along with a member of the main opposition Bangladesh Nationalist Party.
Mr Joarder was hacked to death while sitting outside his shop by assailants who escaped on a motorbike. He spent two weeks in prison in 2012 for allegedly insulting Muhammad.
His killing came just a week after leading gay rights activist Xulhaz Mannan and his friend were brutally murdered in the capital Dhaka.
A Bangladeshi militant group affiliated to al-Qaeda, Ansar al-Islam, said it was behind those killings.
The government has blamed all the attacks on local Islamic groups. It has been strongly criticised for not being able to prevent the violence or bring anyone to justice.
In a speech to mark Labour Day on Sunday, Prime Minister Sheikh Hasina said it was members or supporters of her party who were mostly being targeted by the killers.
Last year, four prominent secular bloggers were killed with machetes.
The four bloggers had all appeared on a list of 84 “atheist bloggers” drawn up by Islamist groups in 2013 and widely circulated.
Who exactly is behind the attacks remains murky. Bangladesh has myriad extremist groups and there have been few convictions over the attacks.