A group of attackers armed with machetes killed a blogger in Bangladesh on Friday, making it the fourth such deadly attack in the country this year.

The blogger, Niloy Chatterjee, 40, who advocated secularism and freedom of expression, was best known by his pen name, Niloy Neel. He was killed at his apartment in the capital, Dhaka, according to police official Mustafizur Rahman.

Ansar Al-Islam, Al-Qaeda’s branch in Bangladesh claimed responsibility for the attack, English-language newspaper The Daily Star reported, citing an email sent to the Bangladeshi press.

“We are speechless. He was demanding justice for killing of other bloggers,” said Imran Sarker, the head of a network of activists and bloggers. “Who will be next for demanding justice for Niloy?”

Sarker told Agence France-Presse (AFP) news agency that attackers entered Chatterjee’s fifth floor apartment then “hacked him to death.” Muntashirul Islam, a deputy police commissioner, told AFP that “there were six people who knocked his door, saying that they were looking to rent a flat.“

“Two of them then took him to a room and then slaughtered him there,” Islam said. “His wife was in the flat, but she was confined to another room.”

Chatterjee, whose last name has also been reported as Chowdhury and Chakrabarti in media reports, was a critic of religion. He focused his writing on human rights, minorities and the war crimes tribunal set up to punish those who allegedly collaborated with Pakistani soldiers during Bangladesh’s war of independence from Pakistan. Bangladesh says more than 3 million people were killed and 200,000 women were raped during the nine-month war, which ended in December 1971.

Critics say the government has shown indifference to the recent attacks on defenders of secularism and free expression. “Niloy was an activist of the pro-liberation platform. He was killed because there is no justice in the country,” Sarker told The Daily Star. “I am embarrassed to raise any demand to the government for the arrest of the perpetrators, as bloggers are being killed, but no killer has yet been tried.”

Secular writers in Bangladesh have been targeted in recent years, even as the government attempts to crack down on groups seeking to promote their version of Sharia. Most of the 160 million people in Bangladesh are Muslim, but the country’s constitution holds that it is a secular country.

Most secular bloggers have either gone into hiding or have fled abroad, and they often use pseudonyms in their posts. Activist groups say they fear that hit squads are targeting the bloggers and have access to their full names and addresses.

In February machete-wielding assailants hacked to death a U.S. citizen of Bangladeshi origin and a critic of religious militancy, Avijit Roy, and seriously injured his wife and fellow blogger, Rafida Bonya Ahmed. They were attacked in Dhaka after leaving a book fair. On March 30, Washiqur Rahman, another blogger who aired his outrage over Roy’s death on social media, was killed in a similar fashion. Ananta Bijoy Das, was attacked by machete-wielding attackers and killed in the northeastern district of Sylhet on May 12.

Chatterjee was one of hundreds of bloggers driving a movement demanding the death penalty for those accused of atrocities during the war. A tribunal, opened by Prime Minister Sheik Hasina in 2010, has since convicted several senior leaders of Jamaat-e-Islami of various crimes. The group in 1971 opposed independence for Bangladesh, then known as East Pakistan. They denied wrongdoing. So far, two people have been put to death since the tribunals were set up.

However, the main opposition, the Bangladesh Nationalist Party, led by former Prime Minister Khaleda Zia, has criticized the tribunal, saying it is politically motivated and intended to weaken the opposition. Jamaat-e-Islami is the main political ally of Zia’s party.

Al Jazeera and wire services