Counterterrorism officials yesterday claimed that they arrested an Ansar al Islam militant who along with three others hacked to death writer-blogger Avijit Roy nearly three years ago.

Arafat Rahman alias Siam alias Sazzad, 24, was arrested when he was about to meet some of his accomplices in Savar on Friday night, said Masudur Rahman, deputy commissioner (media) of Dhaka Metropolitan Police.

Siam, an alleged operative of the banned militant outfit's operational wing, is among the six suspected militants, who have been carrying police bounty since May 19 last year.

“He [Siam] was among the four operational operatives who carried out the machete attack on Avijit,” said a counterterrorism official preferring anonymity.

Avijit, a Bangladesh-born US citizen, was hacked to death on Dhaka University campus when he along with his wife Rafida Ahmed Bonya was returning from the Amar Ekushey book fair on February 26, 2015.

Bonya was critically injured in the attack but she survived.

Police claimed that Siam, like several other arrested accused in the case, in his primary interrogation told them that they carried out the attack on Avijit on the instruction of sacked and absconding army major Syed Ziaul Haque, alleged military chief of Ansar al Islam. 

The law enforcers further claimed that Siam also admitted his involvement in the killings of publisher Faisal Arefin Dipan in Shahbagh on October 31 in 2015, blogger Niladri Chattopadhyay Niloy in Khilgaon on August 7 the same year, and LGBT rights activists Xulhaz Mannan and his friend Mahbub Rabby Tonoy in Kalabagan on April 25 last year.

Dipan, the owner of Jagriti Prokashony, published several books by Avijit. 

Meanwhile, a Dhaka court yesterday placed Siam on a five-day remand after police produced him before it seeking a 10-day remand.

Police said they would appeal to the court to show him arrested in the other murder cases as well.

The law enforcers claimed to have arrested 11 suspects, including Siam, in the Avijit murder so far.

Two of them had already given confessional statements before courts.

Abu Siddique Sohel alias Sakib alias Sajid, 34, in his confessional statement on November 6 this year said four assailants, including him, followed Avijit at the book fair while four others, who were waiting outside the venue, took part in the killing mission.

Nine of the arrestees – Sakib, Mojammel Hossain alias Saimun, Shafiur Rahman Farabi, Sadekur Rahman Mithu, Alimul Mallik, Towhidur Rahman, Julhaj Biswas, Sabez Ali and Jafran -- are now behind bars.

Another suspect Abul Bashar, brother of Ansarullah Bangla Team's spiritual leader Jashim Uddin Rahmani, died in jail custody while undergoing treatment at Dhaka Medical College Hospital.

Besides, Sharif alias Saleh alias Arif alias Hadi, a suspect in the Avijit murder, was killed in a “gunfight” with law enforcers in the city's Khilgaon on June 19 last year.

Police have collected 11 kinds of evidence from the killing spot and sent those to the DNA lab of the US Federal Bureau of Investigation. However, the DNA profiles did not match with those of the arrestees.