DHAKA, (AA): Publisher Faisal Arefin Dipan was killed in a knife attack Saturday at his office in Bangladeshi capital Dhaka, police said.

Dipan, 43, had published a book authored by secular blogger Avijit Roy, who was killed in February.

Another publisher who worked with Roy, Ahmedur Rashid Tutul (43), was also attacked in a similar incident in the afternoon at his office in the capital.

Radical group Ansar al Islam allegedly claimed responsibility for the twin attacks on social media Saturday evening.

Doctors declared Dipan dead at hospital. His body is kept in the morgue for a post-mortem on Sunday morning.

While it has yet to be confirmed whether Dipan had received any death threats, he had written a status message on his Facebook page on Oct. 21 that said: “Rest in Peace Faisal Arefin Dipan…”

Dipan’s father Fazlul Haque, a professor at the University of Dhaka, told reporters: “He may have been killed for publishing Avijit Roy’s book.”

“He had no enemies,” he said, “but as killers attacked another publisher who published Avijit’s book, it is not difficult to assume that they also killed my son.”

Dhaka Metropolitan Police’s deputy commissioner Muntasirul Islam told reporters at the hospital: “The attack was pre-planned and the motive of the murder is yet to be understood, but it seems there was more than one murderer involved in this killing.”

The deadly attacks put a strain on the country’s intellectuals. Condemning the murder, writer and activist Shahriar Kabir said: “it seems that the murderers wanted to send a message to free thinkers about their possible fate.”

At least four bloggers were killed this year in Bangladesh, including Roy in February, Washikur Rahman in March, Ananta Bijoy Das in May and Niladri Chattopadhyay in August. It was another radical group, Ansarullah Bangla Team, that claimed to have killed Roy.