Publisher Faisal Arefin Deepan was found hacked to death inside his office in the Bangladeshi capital Dhaka, on 31 October, say police. It was the second such attack in the city on the same day, as earlier a publisher and two writers were stabbed and shot, and are now in a critical condition in hospital, police confirmed.

Deepan, of the Jagriti Prokashoni publishing house, had filed a complaint with police after being threatened with death on Facebook, his friends said.

"I saw him lying upside down and in a massive pool of blood... He is dead," Deepan's father, Abul Kashem Fazlul Haq, told AFP. Blogger Imran H Sarker and medical sources confirmed Deepan's death to DW journalist Arafatul Islam. Deepan was the only son of Haq, a well-known writer and professor of Dhaka University's Bengali department.

He had published Avijit Roy's book Biswaser Virus (Virus of Faith). The book was popular with secular thinkers and intellectuals, but had upset Islamist radicals, who are suspected to be involved in his murder, according to Bangladesh News.

Roy was murdered by machete-wielding killers in the Dhaka University campus in February 2015 during the Amar Ekushey Book Fair. Son of well-known physicist Ajoy Roy, Avijit was a US citizen and outspoken blogger who wrote about rationality and science.

Though no group has claimed responsibility for the serial attacks on the two publishers on Saturday, bloggers and online activists are blaming Islamist radicals for them. Dhaka police spokesperson Muntasirul Islam told that Deepan's was a "pre-planned murder". "It seems more than one assassin were involved in the murder."

Earlier in the day, publisher Ahmed Rahim Tutul and two writers were shot and stabbed by three men in the office of the Shudhdhoswar publishing house in Dhaka, said police officer Abdullah Al Mamun.

The assailants locked the wounded men inside the publishing house offices before fleeing. "We had to break the lock to recover them," Local police chief Jamal Uddin Meer said.

The two writers were identified by police as Ranadeep Basu and Tareque Rahim. All three of the victims were hospitalised, and Tutul is in a critical condition. Protesters gathered outside at the hospital where the victims were taken to demand the government does more to protect the country's secular bloggers.

Bangladesh has been hit by a number of attacks this year claimed by Islamic extremists, including the blogger murders and, more recently, the killing of two foreigners — an Italian aid worker and a Japanese agricultural worker. A bomb attack on 24 October targeted thousands of Shiite Muslims in Dhaka, killing a teenage boy and wounding more than 100 people

The Islamic State group claimed responsibility for the attacks on the two foreigners and the bombing, but Bangladesh's government has rejected that the extremist Sunni militant group has any presence in the country. Local Islamist group Ansarullah Bangla Team claimed responsibility for the blogger killings and recently threatened to kill more bloggers.