The Rapid Action Battalion (Rab) on Wednesday arrested five people over the killing of a woman and her three children at Abdar of Sreepur upazila.
The arrestees were identified as Md Kazim Uddin, 50, Md Hanif, 32, Md Basir, 26, Md Helal, 30, and Md Elahi Mia, 35.
Lt Col Sarwar Bin-Kashem, director of legal and media wing of Rab, confirmed the matter at a media briefing at the force's headquarters.
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He said the conducted drives at different areas of Shreepur early Wednesday acting on tip-offs and arrested the accused.
The accused killed the four victims after committing robbery at their house, Kashem said.
They also raped the female victims, he added.
Police recovered the bodies of the woman and her three children from their house at Abadar on April 23.