NEW DELHI: The Islamic State claimed responsibility for hacking to death a University professor in the city of Rajshahi. English professor Rezaul Karim Siddique, 58, was attacked by machete wielding assailants, as he walked to the bus station from his home.

"By examining the nature of the attack, we suspect that it was carried out by extremist groups," Rajshahi Metropolitan Police commissioner Mohammad Shamsuddin told AFP.

The Islamic State was quick to claim responsibility. "Islamic State fighters assassinate(d) a university teacher for calling to atheism in the city of Rajshahi in Bangladesh," ISIL's Amaq news agency said.

Whether the claims by the Islamic State are true or not, Islamist groups have been known to attack professors and bloggers and Bangladesh, with the killings largely following a pattern where assailants use machetes and the victims are hacked to death in public spaces.

Professor Siddique, is the fourth professor from Rajshahi University to be killed by Islamists.

People close to Siddique said he had never spoken out against religion, but he may have been targeted for his role in leading music and literature groups. "As far as I know, my husband didn't have any personal enmity with anyone," his wife, Hosne Ara, told the BBC.

Officials say that there are no suspects as yet, but the attacks follows the style of Islamist groups active in the country. Just earlier this month, secular blogger -- Nazimuddin Samad -- was hacked to death in Dhaka. Samad, a 28 year old law student had criticised elements of radical Islamism on his Facebook page, had been on a hit list of 84 atheist bloggers that a group of radical Islamists had drawn up and sent to the interior ministry.

Although Bangladesh is technically a secular state, targeting of atheist bloggers has been a huge concerns -- as 2015 saw multiple such attacks, with secular bloggers and writers being hacked to death by machete wielding assailants. Protesters -- 300 of whom took the streets after Samad’s murder -- have accused the government and police of fostering a climate of impunity that makes such brutal crimes not just possible, but frequent in the Muslim majority country.

Maruf Rosul, one of the Ganajagaran Mancha activists, told the Guardian: “The government is creating impunity to all the offences by not bringing the perpetrators to book. “Instead of pointing blame at different outfits, the government should identify the perpetrators and bring them to justice.”

In 2015, Bangladesh witnessed multiple similar attacks on secular writers, bloggers and others. In October, a publisher of secular books was hacked to death, while two other writers and a publisher were stabbed and shot at a publishing house in a separate attack in Dhaka. The body of Faisal Abedin Deepan, of the Jagriti Prokashoni publishing house, was found inside his office, after Deepan had filed a complaint with the police following death threats and abuse received on facebook.

On the same day in October, publisher Ahmed Rahim Tutul was attacked in the office of the Shudhdhoswar publishing house and seriously wounded. Two other writers were seriously wounded in the attack.

Both Deepan and Tutal had published books by Bangladeshi-American writer and blogger Avijit Roy, who was hacked to death in February the same year. A month later, blogger Washiqur Rahman was killed. Blogger Ananta Bijoy Das was killed in May. In August, Niloy Neel, another secular blogger was hacked to death.

In all cases, the Bangladesh government did little to catch the attackers. All four men were killed in a similar fashion -- hacked to death with sharp weapons. All of them were killed inside or near their homes. Further, all four were critical of religious intolerance, a sensitive issue in Bangladesh which although technically a secular country is gripped by religiously-motivated politics and violence.

Niloy Neel was murdered after the gang broke into his apartment in the capital's Goran neighbourhood, according to the Bangladesh Blogger and Activist Network which was alerted to the attack by a witness. Neel's name was Niloy Chowdhury, but he used the former name in the blogging community,Dhaka Tribune reported, Neel used to write about the need for capital punishment for 1971 war criminals, the report said.

In an earlier attack, blogger-activist Ananta Bijoy Das was murdered in northeastern Sylhet in Bangladesh by unknown assailants.

Das, in fact, wrote blogs for Mukto-Mona, a website once moderated by Roy. Police said that Das was attacked by masked men with machetes in broad daylight, as he left his home for work. Local police officer Mohammad Rahamatullah told Reuters that Das "came out of his house and what we came to know from the local people who are witnesses, was that four miscreants chased him and killed him near his house".

In all cases, the Bangladesh government and police came under scrutiny. Roy’s death, for instance, prompted the country’s Law Commission to comment on the “general” and “helpless” way people are being targeted in the country that has, in turn, compromised faith in the judicial system. Roy’s wife, who suffered head injuries and lost a thumb in the attack, had initially pointed to police failure in preventing the attack. “While Avijit and I were being ruthlessly attacked, the local police stood close by and did not act,” Rafida told Reuters. Now, we demand that the Bangladeshi government do everything in its power to bring the murderers to justice.”

Roy’s father, Ajay Roy, also accused the police of negligence in the crime and said officers allowed the attackers to escape, adding that he was "not satisfied" with the investigation.

Tragically, five deaths were not an aberration. They follow a string of attacks on writers, bloggers, professors and journalists in the country.

According to the “2014 World Press Freedom Index” released by Reporters Without Borders in January this year, Bangladesh ranked a low 146 of 180 nations. Ahmed Rajib Haider, an atheist blogger was hacked to death on February 2013, by machete-wielding activists from a militant group associated with the Jamaat-e-Islami party. Haider, an architect by profession, ran a blog that was instrumental in demanding trials for the perpetrators of the mass killings during the Bangladesh Liberation War of 1971, a move that was widely seen as aimed at radical Islamists.

Sagar Sarowar and Meherun Runi, two well-known married Bangladeshi journalists were stabbed to death in February 2012; the motive is still to be determined. Another blogger, Asif Mohiuddin, was stabbed and accused of blasphemy.

(Main photo: Bangladeshi activists take part in a torch-lit protest against the killing of bloggers and secular writers).