A Bangladeshi-American blogger, well-known for his writing opposing religious fundamentalism, was hacked to death by unknown assailants in the Bangladeshi capital, Dhaka, according to media reports.

Avijit Roy, the founder of the Mukto-Mona (Free-mind) blog, and his wife, Rafida Ahmed, where pulled from a rickshaw taxi in the city by two armed assailants, who proceeded to attack the pair violently.

Local police chief, Sirajul Islam, told The Associated Press that the assailants used cleavers to attack the couple.

"Several attackers took part in the attack and at least two assailants hit them directly," Islam said, adding that two blood-stained cleavers were found after the attack. Roy's wife survived the attack, but sustained severe injuries, including the loss of a finger.

No individual or group has claimed responsibility for the attack, but Roy's father said that his son had received several “threatening” messages from religious hardliners unhappy with his work, according to AFP. Hardline Islamists in the Muslim-majority nation have long demanded the public execution of atheist bloggers and sought new laws to combat writing critical of Islam, the agency added.

Roy had penned a number of controversial books, including Samakamita (Homosexuality) and Obisshahser Dorshon (Philosophy of Atheists), his publisher Ahmed Rashid Tutul said, according to Deutsche Welle.

"Roy became target of the fundamentalists groups when his books ... hit the stands a few years ago," Tutul added.

An Islamist blogger in the country had issued death threats against the founder of online retailer Rokomari.com, in order to pressure the stop selling Roy's books, Bangladesh News24 reported. They subsequently ceased to sell the author's work in 2014.

Roy is the second Bangladeshi blogger to have been murdered in the last two years, and the fourth writer to have been attacked since 2004, AFP added.

Police commander Islam said that authorities “do not have any clear idea about the attackers. But, the police is suspecting that those, who attacked Humayun Azad, might be behind this as the attacking style suggested similarity,” the Dhaka Tribune reported.

Humayun Azad was a Bangladeshi author and scholar who was found dead in his apartment in Germany in 2004. His family alleged that religious extremists who had previously threatened to kill him had a role in his death.