AFP/Dhaka

Secular activists marched Wednesday through the Bangladeshi city of Sylhet to demand justice for a rationalist blogger hacked to death, the third such attack by suspected Islamists since February.

Scores of activists, mostly university students, peacefully protested through the northeastern city, accusing the government of failing to protect free thinkers and urging authorities to halt "this evil force".

Wielding machetes, a masked gang killed Ananta Bijoy Das, 33, a banker, editor and blogger, on Tuesday as he headed to work in Sylhet, an attack that fellow writers said highlighted a culture of impunity.

"Murder won't silence our mouths," the protesters chanted as they marched along a key highway and through Sylhet university, a secular bastion.

"We want justice for Ananta and the other bloggers who have been murdered by Islamist militants. The government must crush this evil force," Debashish Debu, a secular activist who joined the protest, told AFP.

Das was the third blogger killed in the Muslim-majority nation since February when Bangladeshi-born US citizen Avijit Roy was hacked to death in the capital Dhaka.

The deaths have sparked international condemnation, with Washington on Tuesday calling on Dhaka to bring perpetrators of the latest killing to justice.

The activists had called for a strike in Sylhet on Wednesday, although police said offices and schools were mostly open and traffic was running almost as normal.

"Scores of young protesters held two marches in support of the strike," deputy commissioner of police Faisal Mahmud told AFP, adding pro-government students also barricaded a road in protest at the murder.

Mahmud said police suspected Islamist militants were behind Tuesday's killing although there have been no arrests so far.

"There is a similarity of this murder to the previous murders of bloggers. We suspect Islamist militants could be behind the murder," Mahmud told AFP.

Fellow writers have said Das had been on a hit-list drawn up by militants who were behind the recent killing of blogger Roy.

Friends said Das was an editor of a quarterly magazine called Jukti (Logic) and headed the Sylhet-based Science and Rationalist Council.

They said he had received threats from Islamists after he regularly blogged for a website called Mukto-Mona, founded and moderated by Roy, in which criticised aspects of Islam and  Hinduism.

New York-based Human Rights Watch said the latest killing was part of an "alarming" trend of violent intolerance of religious freedom and speech in Bangladesh.

"This pattern of vicious attacks on secular and atheist writers not only silences the victims but also sends a chilling message to all in Bangladesh who espouse independent views on religious issues," said Brad Adams, Asia director at HRW.