This style of attack surprisingly resembles those carried out by militants where upper parts of the body, particularly head and neck, were the main targets.
Investigations into deadly assault on professors Muhammad Yunus and Humayun Azad and blogger Ahmed Rajib Haider point to the involvement of religious zealots.
Dhaka Medical College Forensic Department’s Assistant Professor Dr Sohel Mahmud told bdnews24.com on Friday there were three deep gashes on the right side of Avijit’s head caused by a sharp weapon like a machete.
He added the gashes were parallel, only half inches from each other and strongly struck, without overlapping one another.
The blows had cut through the skull and reached the brain causing excessive bleeding. There were also blows on the back and over the left eyebrow, he added.
The severity of the blows on the back of the head and excessive bleeding caused the death, Dr Mahmud believed.
“This is the handiwork of a professional. They knew where to hit to kill a man. They were very skilled and ferocious,” the doctor said, adding it was impossible to carry out such an attack without ‘planning, skill and brutality’.
Shahbagh police's SI Subrata Haldar did an inquest (Surathaal) on the body before the post-mortem examination.
He said one of the wounds in the back of the head was three inches long and the other six inches. "Both of them are nearly two inches deep."
A bio-engineer and a naturalised US citizen, writer Avijit Roy was hacked to death on the street opposite the the Dhaka University Central Mosque when he along with his wife was returning from the Amar Ekushey Book Fair on Thursday night.
His wife and fellow blogger Rafida Ahmed Bonya was seriously injured as she tried to save Avijit.
Religious radicals have been threatening Avijit for his active campaign against Islamist extremism.
He was a regular bdnews24.com columnist and the founder of the popular blog, Mukto-Mona.
Avijit’s father professor Ajay Roy filed a case with Shahbagh police over the murder on Friday, accusing unnamed assailants.
He said extremists were behind the murder and “Jamaat(-e-Islami) has backed them”.
Police are yet to make any breakthrough in the case. No one has been arrested or detained. Two machetes were recovered from the crime scene.
Thursday’s attack bore a striking similarity to the one on legendary writer Humayun Azad in 2004.
Militants also hacked blogger Ahmed Rajib Haider to death in a similar attack near his home in Dhaka’s Mirpur in February 2013.
Islamist radicals had attacked other secular bloggers like Ashraful Alam and Asif Mohiuddin after the Shahbagh agitation polarised opinions in Bangladesh.
Islamist blogger Farabi Shafiur Rahman had allegedly threatened Avijit Roy with death once he returned home.
Farabi has also been demanding that Rokomari.com, an online shopping portal, stop selling Avijit Roy's books.
Police had arrested Farabi in connection with Rajib Haider’s murder on charges of incitement, but he managed to secure bail.
Islamist group 'Ansar Bangla 7' in a series of tweets from its Twitter handle has described the murder of Avijit Roy as an achievement.
One such tweet described the murder as a punishment for Avijit's "crime against Islam".
The first tweet appeared around midnight on Thursday, after the attack.
Messages included "Allahu Akbar... A great success today here in Bangladesh."