John Bacon, and Oren Dorell

USA TODAY

A branch of al-Qaeda claimed responsibility Tuesday for the fatal stabbing of a U.S. government employee in Bangladesh who was editor of the South Asian nation's first LGBT magazine.

Ansar-al Islam, the Bangladeshi branch of al-Qaeda on the Indian subcontinent, said in a Twitter message Tuesday that it was responsible for the killings. It said the two were targeted because they were “pioneers of practicing and promoting homosexuality in Bangladesh” and were “working day and night to promote homosexuality."

A group of attackers stormed the home of Xulhaz Mannan, a staffer for the U.S. Agency for International Development, stabbing him and friend Tanay Majumder to death in the capital Dhaka on Monday. Mannan was a senior editor of Roopbaan, a magazine launched in January 2014 that takes its name from a Bengali folk character.

Police said five or six assailants, dressed in T-shirts and jeans and posing as delivery men, stormed Mannan’s first-floor apartment about 5 p.m. local time. The victims were stabbed in their heads and necks, a method used in attacks on other secular writers, bloggers and teachers in recent months, bdnews24.com reported. Witnesses told the website the attackers shouted "Allahu Akbar" and fired guns as they fled.

A police officer and a security guard in Mannan's building were wounded, police said. A pistol, five rounds of ammunition and some clothes linked to the killers were found at the crime scene, police told the Bangladesh national news agency.

"We have started investigation into the matter with utmost sincerity and hoped to capture the culprits at the shortest possible time," police said in a statement.

Editor of LGBT magazine hacked to death in Bangladesh

The attack came two days after a Bangladeshi professor was hacked to death in a murder claimed by the Islamic State. Last year, at least four secularists were similarly killed in the country. In August, blogger Niloy Neel was hacked to death in his Dhaka home. In May, blogger Ananta Bijoy Das was killed by masked men with machetes in Sylhet in northeast Bangladesh. In March, blogger Washiqur Rahman, was hacked to death in Dhaka, and in February blogger Avijit Roy was killed in the capital city.

The government of Bangladesh condemned all the slayings, blaming them on incitement by the country's Islamist political opposition. Amnesty International said this latest in a series of killings "underscore the appalling lack of protection being afforded to a range of peaceful activists in the country."

USAID administrator Gayle Smith described Mannan as a "dedicated and courageous advocate for human rights" who worked to make society more inclusive.

"We condemn this cruel and inhumane act of violence and add our voices to all those calling to bring his cowardly attackers to justice," Smith said.

The U.S. State Department condemned the "inexcusable" murder, and the U.S. government is offering to support Bangladeshi authorities to make sure those responsible are held accountable, department spokesman John Kirby said.

Contributing: Jane Onyanga-Omara