DHAKA, Jan. 16 (Xinhua) -- The Bangladeshi police said on Wednesday they had arrested one of the key suspects in connection with the sensational murders of an editor and his friend.

"The suspect, Asadullah, was detained on Tuesday evening," Monirul Islam, chief of the Counter Terrorism and Transnational Crime Unit, told reporters on Wednesday.

He said Asadullah, 25, is one of the seven killers who were captured by a closed-circuit camera while they were fleeing the crime scene.

Asadullah has been identified as a member of banned militant outfit Ansarullah Bangla Team.

With the latest, he said, four accused in the double murder case have so far been arrested.

Machete-wielding assailants forcibly entered the house of Xulhaz Mannan who used to edit "Rupban," Bangladesh's first magazine for the LGBT (lesbian, gay, bisexual and transgender) community, on April 25, 2016 in central Dhaka's Kalabagan area.

The assailants stabbed Mannan and his friend Tonoy Fahim, leaving them dead on the spot.

Mannan, who previously worked as a protocol officer in the U.S. embassy in Dhaka, and his friend were killed for their alleged anti-Islamic activities, Islam said earlier.

A number of secularist writers, bloggers and publishers in Bangladesh have been killed or seriously injured in attacks perpetrated by Islamist extremists since 2013.