A gang armed with machetes hacked a secular blogger to death at his home in Dhaka Friday, sparking protests in the capital over the fourth such murder in Bangladesh this year. Niloy Chakrabarti, who used the pen-name Niloy Neel, was killed after the gang forced its way into his apartment, according to the Bangladesh Blogger and Activist Network, which was alerted to the attack by a witness. "They entered his room in the fifth floor and shoved his wife aside and then hacked him to death. He was a listed target of the Islamist militants," the network's head, Imran H. Sarker, told AFP. Police confirmed Chakrabarti, 30, had been murdered at his home in the capital's Goran neighbourhood by a group of four people who had pretended they were looking for somewhere to rent. "Two of them then took him to a room and slaughtered him there," deputy police commissioner Muntashirul Islam told AFP, adding that his wife had been "confined to another room" during the attack. Asha Moni, wife of the slain blogger, later told reporters that one of the young men attacked him shouting "Allahu Akbar (God is greatest)". Moni said she pleaded with the assailants not to kill her husband but the attackers dragged her to a veranda and confined her there, according to online newspaper bdnews24.com. The Bangladesh branch of Al-Qaeda in the Indian Subcontinent (AQIS), Ansar al-Islam, claimed the killing and warned of more to come, according to monitoring group SITE. "If your 'freedom of speech' maintains no limits, then widen your chests for 'freedom of our machetes'," the group, which also claimed to have murdered secular blogger Washiqur Rahman in March, said in posts on Twitter and Facebook. - Bloggers in hiding - Chakrabarti is the fourth secular blogger to be killed in the Muslim-majority nation since February, when Bangladeshi-born US citizen Avijit Roy was hacked to death in Dhaka. Roy's wife was also badly wounded in the attack. The other victims include 27-year-old Rahman who was killed in Dhaka four months ago and Ananta Bijoy Das, who was attacked in May by a group wielding machetes in the northeastern city of Sylhet. In a Facebook post on May 15, Chakrabarti said he had been followed by two young men after protesting over Das's murder, but police refused to register the complaint and instead told him to leave the country. Most secular bloggers have gone into hiding, often using pseudonyms in their posts. And at least seven have fled abroad, according to a Canada-based atheist blogger Farid Ahmed, who helped several of them. Activist groups say they fear Islamist hit squads have lists with the bloggers' real names and addresses. Asif Mohiuddin, another blogger who himself survived an attack in Bangladesh in 2013, described Chakrabarti as an atheist "free thinker" whose posts appeared on several sites. "He was critical against religions and wrote against Islamist, Hindu, Christian and Buddhist fundamentalism," Mohiuddin, who is now based in Berlin, told AFP by phone. Police said Chakrabarti had been one of the organisers of the large-scale protests in 2013 against Islamists convicted of war crimes dating back to the 1971 conflict when Bangladesh seceded from Pakistan. - 'Chilling effect' - Immediately after Chakrabarti's murder, hundreds of secular activists joined a protest march in the city's Shahbagh Square, which was also the venue for the demonstrations two years ago. "We're protesting a culture of impunity in Bangladesh. One after another, bloggers are being killed and yet there is no action to stop these murderers," said protester Sarker of the Bangladesh Blogger and Activist Network. Amnesty International said the government had to do more to stop "this spate of savage killings". "These especially brutal killings are designed to sow fear and to have a chilling effect on free speech," said David Griffiths, the rights group's South Asia research director. "The price for holding opinions and expressing them freely must not be death. The Bangladeshi authorities now have an urgent duty to make clear that no more attacks like this will be tolerated." The US State Department also condemned what it dubbed a "cowardly murder". "We offer our condolences to his family and our support to the Bangladeshi people," said a statement. "This heinous act once again underscores the need to work together to counter violent extremism." Bangladesh banned the hardline Islamist group Ansarullah Bangla Team (ABT) following Das's murder after facing accusations that too little was being done to stop such attacks. In a recent petition to Prime Minister Sheikh Hasina, authors including Salman Rushdie and Margaret Atwood called on her government "to do all in their power to ensure that the tragic events... are not repeated". Bangladesh is an officially secular country, but more than 90 percent of its 160 million people are Muslim.