Investigators probing the murder of writer, publisher Shahjahan Bachchu have claimed that there is a remarkable headway in the case.

A top law enforcement official told the news agency that investigators are almost confirmed about involvement of a religious extremist group in the killing of Bachchu, who had reportedly been on the hit list of the group since 2015.

However, the investigators refrained from naming the group as they are expecting to arrest the militants involved with the killing soon.

Shahjahan Bachchu, 60, an outspoken proponent of secular

principles and owner of the publishing house "Bishaka Prokashoni", was gunned down in his ancestral village Kakaldi under Sirajdikhan Police Station in Munshiganj district on June 11 evening.

He had gone to meet friends at a pharmacy near his home, when four attackers on

two motorcycles swooped on him. They blasted a crude bomb outside the pharmacy, creating panic, and dragged him out of the shop and shot him.

Victim's second wife Afsana Jahan filed a case with Sirajdikhan Police Station, accusing four unidentified people on June 12.

Although no group has claimed responsibility, law enforcement agencies are investigating the case, considering it a possible targeted attack by extremists.

Bachchu, also a former general secretary of Communist Party of Bangladesh's (CPB) Munshiganj district unit, had previously received threats from extremist groups over his writings on religious topics.

Munshiganj's Superintendent of Police (SP) Md Zaidul Islam said there was a major headway in the investigation into the case and the killers will be arrested shortly. Another investigator, wishing anonymity, hinted at extremists becoming hostile to Bachchu over some comments made by the slain publisher that they considered tantamount to demeaning religious beliefs.

Alter investigation, law enforcers are almost confirmed that religious extremist groups were involved in the killing, he said.

Attacks, carried outby Islamist militants, came to the fore after the murder of atheist writer and blogger Avijit Roy near the Ekushey Book Fair venue in Dhaka on February 26, 2015. Avi jit's publisher Faisal Arefin Dipan was also hacked to death on October 31 the same year.