Ansar-al Islam, the Bangladeshi branch of al-Qaeda, claimed responsibility for the hacking death of Bangladeshi LGBT activist Xulhaz Mannan on Tuesday, calling the brutal murder a "blessed attack" in an announcement posted to Twitter.

Mannan and a friend who was also killed in the attack were tailed by al-Qaeda operatives in the days before their slayings because they were "pioneers of practicing and promoting homosexuality," according to The AP.

Mannan, the editor of Bangladesh's first gay rights magazine, Roopbaan, wrote unapologetically about his experience being openly gay in the country to give a voice to its small and closeted LGBT population.

The AP reports:

Mannan had written openly about the frustration of living "in the closet" as a gay man in Bangladesh, where homosexual relations are considered a crime. In a May 2014 blog, he said gays and lesbians in Bangladesh experience "A country where the predominant religions say you are a sinner, the law of the land says you are a criminal, the social norms say you are a pervert, the culture considers you as imported."

Earlier this month, Mannan even tried to organize a gay rights rally in the capital before he and three others were briefly detained by police.

Homosexuality is illegal in Bangladesh but pressure from officials abroad has forced the government to investigate the murders closely.

On Thursday, Secretary of State John Kerry placed a call to Prime Minister Sheikh Hasina to offer U.S. support for an investigation.

“The secretary urged Prime Minister Hasina to ensure a thorough investigation of all of these incidents, and to redouble law enforcement efforts to prevent future attacks and protect those who are at risk,” the State Department said in a statement.