Roy’s family and Bangladeshi investigators said they suspected extremists behind the murder.
If the claim is true, it means the militant organisation has operatives in Bangladesh who have regularly targeted secular writers.
However, the security forces have always denied existence of the terrorist organisation in Bangladesh.
Unidentified assailants hacked Roy and his wife Rafida Ahmed Bonya, both US citizens of Bangladeshi origin, on Feb 26 near Dhaka University’s TSC intersection.
Roy, a bioengineer by profession, had been threatened on social media for his secular writings.
His wife Bonya survived but lost a thumb.
In an op-ed column, she wrote radical organisation ‘Ansar Bangla 7’ had claimed responsibility for the attack.
According to a report on SITE Intelligence Group’s website, Al-Qaeda in the Indian Subcontinent (AQIS) leader Asim Umar also claimed credit for the murder of other “blasphemers” in Bangladesh and in Pakistan.
State Minister for Home Affairs Asaduzzaman Khan Kamal declined comment on the AQIS claim.
"I've learnt it from journalists," he said. "I don't want to make any official comments just now."
The Detective Branch (DB) of police, investigating Roy's murder, were unavailable for comment.
Many secular blog activists have come under attack in Bangladesh.
A month after Roy’s killing, another blogger Oyasiqur Rahman Babu was killed in similar fashion in Dhaka.
Although the DB say they suspect the attacks are connected, they failed to identify any of the attackers.
Extremist group ‘Ansarullah Bangla Team’ came to limelight in recent times after attacks on blog activists. Its chief Mufti Jashim Uddin Rahmani has been charged with the killing of blogger Ahmed Rajib Haider in 2013 in Dhaka.
DB officials say Ansarullah closely follows al-Qaeda in its operations although they have no confirmation of the international militant group’s activities in Bangladesh.
In February last year, a purported audio tape from al-Qaeda chief Ayman al-Zawahiri dubbed Bangladesh government “anti-Islam and secular”.
He called on Bangladeshi Muslims to “wage a battle to protect Islam”.
Then the inspector general of police Hassan Mahmood Khandker said they were looking into the matter.
Later in September that year, Zawahri announced formation of al-Qaeda’s Indian branch to “spread Islamic rule and raise the flag of jihad" across the subcontinent.
He described it as a good news for Muslims "in Burma, Bangladesh, Assam, Gujarat, Ahmedabad, and Kashmir" saying the new wing would rescue them there from ‘injustice and oppression’.
Bangladesh has maintained that it is capable of tackling militancy.