UPDATE
A suspected Islamic militant has been arrested for his alleged involvement in the killing LGBT activists Xulhaz Mannan and Tonoy Mahbub, Bangladesh police said.
Police named the man as Shariful Islam Shibab, a former member of a banned Islamic group Harkatul Jihad who joined another militant group, Ansarullah Bangla Team, in mid-2015, the Associated Press reported.
Munirul Islam, head Bangladesh police's counterterrorism unit, told a news conference on Sunday that Shibab was arrested in the southwestern district of Kushtia.
Xulhaz Mannan, editor of Bangladesh's only queer publication, Roopbaan, who also worked for the U.S. Agency for International Development, was hacked to death by a group that entered his house in the capital, Dhaka, The Guardian has reported based on police sources.
Mannan, who was killed along with his friend and fellow activist Tonoy Mahbub, was the latest in a string of murders of secular bloggers, journalists, and academics that began last year, several of which ISIS has claimed responsibility for.
On Tuesday, the Bangladeshi branch of al-Qaeda claimed responsibility for the killings, the Associated Press reported.
"I am devastated by the brutal murder of Xulhaz Mannan and another young Bangladeshi this evening in Dhaka," said U.S. Ambassador Marcia Stephens Bloom Bernicat in a statement on the embassy's Facebook page. "Xulhaz was more than a colleague to those of us fortunate to work with him at the U.S. Embassy. He was a dear friend. Our prayers are with Xulhaz, the other victim, and those injured in the attack. We abhor this senseless act of violence and urge the Government of Bangladesh in the strongest terms to apprehend the criminals behind these murders."
At least four were assassinated in 2015, including Avijit Roy, author of a landmark book on homosexuality published in Bangladesh in 2010. Just two days before Mannan was attacked, Rezaul Karim Siddique, an English professor and editor of a literary magazine, was killed by a group of men wielding machetes in the northwestern part of the country. ISIS claimed responsibility for the killing, accusing him of "calling to atheism."
Twenty-six-year-old Nazimuddin Samad, a well-known blogger who spoke out against religious extremism, was killed in a similar assault earlier this month after being named along with 83 others on a list that Islamist militants sent to the country's Interior Ministry of writers they intended to target.
A group of activists founded Roopbaan as a quarterly magazine in 2014, but it was available only through phone orders out of fear of sparking a backlash. When it was launched, those involved in the publication stayed anonymous out of safety concerns.
Bangladesh is a growing target for ISIS. Two weeks ago, the group devoted a significant section in its recent issue of its propaganda magazine, Dabiq, to promote turning Bangladesh into a "strong jihad base" before moving into neighboring India and Burma, where the group says Muslims are oppressed by Hindus and Buddhists.