Speaking to the media on Tuesday after visiting Ekushey Book Fair venue, Commissioner Asaduzzaman Mia said investigators have identified all of those involved in the killing.
"We have arrested eight suspects; the prime suspect Mukul Rana died in a shootout at Dhaka's Meradia. We hope the rest of them will be arrested soon."
Bangladeshi American writer Avijit, who founded the blog ‘Muktomona’ (free thinkers), and his wife Rafida Ahmed Bonya were attacked on the night of Feb 26, 2015.
Avijit suffered a deep gash on his head and died while Bonya survived but lost a finger in the assault.
Islamist zealots had been threatening Avijit, a bioengineer and a naturalised US citizen, for his active campaign against Islamist radicals, for quite some time.
His father Ajay Roy, a well-known physicist who has taught at Dhaka University for a long time, started a police case over the incident.
In the last two years, the Detective Branch pleaded 15 times to the court for extending the deadline to submit the probe report.
A street vendor, who witnessed the murder, had told bdnews24.com that he saw two men hacking Avijit and Bonya with machetes.
Since the killing of Avijit, several others, including online activists, writers, publishers, members from the minority communities have been attacked or killed in similar fashion by machete-wielding attackers, targeting the head to ensure immediate death.
On Jun 19 last year, police released video footage from a CCTV camera showing Avijit and Bonya being followed by a youth on leaving the Ekushey Book Fair.
Hours before the footage was released, police informed the media of a man's death in Dhaka's Khilgaon in what they described as a 'shootout', who the law enforcers later identified as Sharif.
Police had said then the 30-year-old used several other aliases like Sakib, Saleh, Arif and Hadi.
The youth was later identified as Mukul Rana by his family.
On Aug 21 that year, police released six more footages from CCTV cameras around the crime scene, where they identified two other attackers.
DMP Deputy Commissioner Masudur Rahman had said then that they have identified six persons and one of them died in an 'encounter' and that the footages have been released to trace the rest.
Police had then also said a six-member squad of Ansarullah Bangla Team was involved in the attack on Avijit.