The Police Bureau of Investigation on Wednesday claimed that an extramarital relationship was behind the killing of a couple and the death of their unborn child in Ashulia.

The police arrested Moniruzzaman, 44, also known as Hridoy, from Narsinghpur in Ashulia on Tuesday and said he later confessed to the killings in a statement before a court under Section 164 of Bangladesh’s Code of Criminal Procedure.

M N Morshed, superintendent of police at PBI’s Dhaka district unit, confirmed the matter in a press briefing in his office on Wednesday morning.

The victims were Alamgir Kabir, 45, his wife Nazma Khatun, 39, and their unborn child. Nazma was about seven months pregnant, according to investigators.

The PBI investigators believe Nazma had a long-standing relationship with Moniruzzaman, which led to a dispute between him and Alamgir.

According to Moniruzzaman’s court statement, Alamgir and Nazma went to his rented home on the day of the killings and took him to their house, where they confronted him over his relationship with Nazma.

An argument escalated into a physical confrontation, with Alamgir allegedly beating Moniruzzaman and Nazma, PBI said.

Moniruzzaman allegedly kicked Nazma in the abdomen, causing her and the unborn child to die, according to the statement.

When Alamgir then attacked him with a kitchen ladle and a pipe, Moniruzzaman allegedly punched him several times before strangling him with a towel.

After the killings, Moniruzzaman allegedly placed the bodies on a bed, locked the room from the outside, and left the house, investigators said.

The police recovered Nazma’s mobile phone, SIM card, office identity card, and handbag from a rented house based on information provided by Moniruzzaman, PBI said.

The bodies were found on 5 September after residents reported a foul smell coming from a locked room on the second floor of a house in Jamgora. The police broke open the door and recovered the decomposed bodies.

Nazma’s sister, Shapla Begum, filed a murder case with Ashulia police following the discovery of the bodies.

The PBI said it took over the investigation on Tuesday after conducting a shadow investigation following the incident.

‘We are examining whether anyone else was involved in the killings,’ said M N Morshed, superintendent of police at PBI’s Dhaka district unit.

‘Court sent Moniruzzaman to jail’, he added.