Dhaka - Hundreds of mourners have paid tribute to the Bangladeshi-born American blogger who was hacked to death outside a university in Dhaka.

Student activists, human rights advocates and members of the academia joined the family of slain writer Avijit Roy on Sunday, offering flowers on the victim's coffin during a vigil at Dhaka University.

Unknown assailants targeted Roy and his wife Rafida Ahmed, after they attended a book fair at the university on Thursday. Roy died in the hospital while his wife, also a blogger, sustained severe injuries.

The victim's father Dr Ajay Roy, a physics professor at the university, called on Prime Minister Sheikh Hasina to bring the killers of his son to justice, and to "ban" far-right organisations.

"Try the killers of Avijit and all those who were killed in militant attacks. And ban all militant outfits including Jamaat-e-Islami," he said.

The Jamaat, country's biggest Islamic party, was banned from contesting the January 2014 general elections.

The elder Roy also said his son's murder is a reflection of government's failure to prosecute crimes in the country.

Secular bloggers targeted

Avijit's remains was kept at the university for an hour to allow mourners to pay their last respects. Later, his body was taken to the same spot where he and his wife were attacked.

The victim's family said that his body will be donated to Dhaka Medical College Hospital (DMCH) for medical research according to his wishes.

Roy had founded a popular Bengali-language blog - Mukto-mona, or Free Mind - in which articles on scientific reasoning and religious extremism featured prominently.

US State Department spokeswoman Jen Psaki called the fatal attack on Roy "a shocking act of violence" that was "horrific in its brutality and cowardice".

In 2013, religious groups targeted several secular bloggers who had demanded capital punishment for Islamist leaders convicted of war crimes for their involvement in Bangladesh's war for independence in 1971.

Blogger Ahmed Rajib Haider was killed that year in a similar attack near his home in Dhaka after he led one such protest demanding capital punishment.

In 2004, Humayun Azad, a secular writer and professor at Dhaka University, was also attacked by armed men while returning home from a Dhaka book fair. He later died in Germany while undergoing treatment.

Media group Reporters Without Borders rated Bangladesh 146th among 180 countries in a ranking of press freedom last year, according to a Reuters news agency report.