Detectives have arrested three suspects over the killing of Niloy -- one for sending a death threat to the secularist blogger and two for claiming the responsibility for the murder, said a top DB official.

Of the arrested, Mufti Abdul Gaffar, a former madrasa student in Chittagong, in a Facebook post had threatened to hack Niloy to death with a machete around three months before the killing, Monirul Islam, joint commissioner of the Detective Branch of Dhaka Metropolitan Police, told a press briefing at the DMP media centre yesterday.  

The other arrestees are Mortuza Faisal Sabbir, a ward level Shibir leader in Chittagong, and Tarequl Alam, a former general secretary of Sitakunda Shibir.

The duo claimed the responsibility for Niloy's murder in a Facebook post uploaded from a mobile phone, Monirul said.

This is the first time in Bangladesh that any one has been held on charges of claiming responsibilities on the internet for such murders, police sources say.

Tarequl was arrested at Chittagong's Panchlaish on Monday while Gaffar and Sabbir at separate places of Narayanganj the next day. The mobile phone was found from the possession of Sabbir.

They were paraded before the media yesterday.

Monirul said they were yet to confirm whether the arrestees directly took part in the killing.

"They have not yet admitted their direct involvement with the murder. They will be interrogated in remand, if granted," he said. Later in the day, a Dhaka court placed each of them on a five-day remand.

The DB official said the arrestees might have links with the murder even if they were not present at the murder scene that day.

On August 7, unidentified attackers tricked into Niladri Chattopadhyay Niloy' Goran house at capital's Khilgaon posing as potential tenants and then hacked him to death inside his bedroom.

That evening, a group identifying itself as Ansar Al Islam claimed the responsibility for the murder in an email sent out to almost all media outlets.

However, no Facebook post with such claims was reported then.

Replying to a query yesterday, Monirul claimed the duo indeed uploaded a Facebook post claiming the credit for the murder.

The sender of the email had identified himself as Mufti Abdullah Ashraf and claimed to be the spokesperson for “Ansar Al Islam (al-Qaeda in Indian Subcontinent, Bangladesh Chapter)”.

Monirul said they were investigating to find out whether any of the arrestees had any link with Ashraf, or himself was the sender of the email.

Detectives said Gaffar, during the primary interrogations, did not admit that he knew Sabbir or Tarequl.

They claimed Gaffar had been involved in "Jihadist activities" during his study at Al Jameyatul Islamiah Patia Madrasa in Chittagong. He used to run different fake Facebook IDs, including "Islamer Sainik Sotter Loraku" from which the threat was issued to Niloy.

Sabbir worked as administrator of different Facebook IDs and pages that ran Jamaat propagandas against the government in the past while Tarequl is accused in around 20 cases filed for subversive activities and arson attacks on vehicles.