"While Avijit and I were being ruthlessly attacked, the local police stood close by and did not act," Ahmed told reporters.

Ahmed, 36, and her husband, 40, were returning from the country's biggest book fair, the annual Ekushey Boi Mela, when they were pulled from their cycle rickshaw by unknown assailants and set upon with machetes.

Roy died of his injuries while Ahmed, who lost a finger in the attack, was treated in a Bangladesh hospital before being flown out to the United States.

Bangladesh-born Roy, an engineer by profession, migrated to America around 15 years ago. He was best known for his blog "Mukto-Mona" (Free mind), in which he criticized all forms of organized religion, as well as demonstrating for gay and lesbian rights.

protesting against the persecution of gays and lesbians.

He was the author of such books as "Samakamita" (Homosexuality) and "Obishwasher Dorshon" (Philosophy of Atheists) which had made him and his blog hugely contentious in Muslim-majority Bangladesh.

The Rapid Action Battalion (RAB), Bangladesh's elite security force, has arrested an Islamic fundamentalist blogger as the "main suspect" in Roy's murder. Farabi Shafiur Rahman has been remanded to custody for further questioning.

Farabi has been jailed in the past for his connections with an extremist Islamist group. He was also arrested in 2013 for comments made in the social media supporting the murder of blogger Ahmed Rajib Haider but had been released on bail.

According to AFP, RAB claims to have seen correspondence between Farabi and an associate about killing Roy.

Roy, a nominee for DW's 2014 "The Bobs - Best of Online Activism" award, is the second Bangladeshi blogger with atheist leanings to have been killed in the past two years - and the fourth writer to be attacked in the past four years.

Bloggers and online platforms are at the forefront of the battle between progressive-liberal and conservative-religious forces in Bangladesh, a central danger being, as Roy's wife Ahmed pointed out, "a legal culture of impunity, where writers can be killed without the killers being brought to trial."

ac/sms (Reuters, AFP)