Hundreds of protesters have taken to the streets in Bangladesh after a third blogger critical of Islam was hacked to death in public.

Ananda Bijoy Das, 32, an atheist who worked in a bank, was murdered on his way to work in the city of Sylhet in northern Bangladesh.

Das wrote blogs for Mukto-Mona, a site moderated by Avijit Roy, himself killed by men with machetes and knives on his way home from a book fair in Dhaka in February. The site carries posts on subjects such as secular humanism, fundamentalism, politics and Islamic hegemony.

In March another blogger, Washiqur Rahman, was hacked to death by two men with knives and meat cleavers outside his home in Dhaka.

Das was also editor of Jukti science magazine, meaning "Reason", and wrote a book about Charles Darwin.

Mukto-Mona awarded Das its Rationalist Award in 2006 for his "deep and courageous interest in spreading secular and humanist ideals and messages in a place which is not only remote, but doesn't have even a handful of rationalists.."

Sylhet's police commissioner Kamrul Ahsan said Das was attacked early in the morning by four masked men wielding cleavers and machetes. There were few witnesses.

The BBC reported that Das had been refused a visa by Sweden after he was invited to attend a press freedom event by the Swedish branch of Pen, the writers' organisation. The Swedish embassy in Dhaka had feared he would not return home. Pen was submitting an appeal when Das was murdered, and has demanded an explanation from Sweden's government.

Other bloggers have also died in suspicious circumstances.

Imran Sarker of the Blogger and Online Activists Network in Bangladesh said: "It's one after another after another. It's the same scenario again and again. It's very troubling."

Twitter accounts celebrated the latest killing.

"What a blessed news to wake up to? We won't let the kuffar sleep comfortably in their mansions!!" said one. Another said: "Stay tuned for next target... "

Bangladesh is officially a secular country but hardline Islamists are gaining influence. No-one has been arrested for any of the murders.