Dinajpur: Police detained a sister and brother-in-law of Obaidul, the accused killer of Willes Little Flower School and College student Suraiya Akhter Risha, from Niratongi village in Birganj upazila on Monday evening.

The arrestees are M Khadiza Begum, 36, and her husband Khadimul Islam, 46, of the village.

Birganj police officer-in-charge Abu Akkas Ahmed said a police team of Ramna Police Station under Dhaka Metropolitan Police, led by sub-inspector Mosharraf Hossain, conducted a drive at the Niratongi village and arrested the couple.

Later, the arrestees were taken to Birganj Police Station for interrogation, he told UNB.

Suraiya Akhter Risha, 14, daughter of Md Ramzan Ali of Bangshal of old Dhaka and an eighth-grader of Willes Little Flower School and College, was stabbed in front of her educational institution at Kakrail in the capital on 24 August.

Risha’s mother filed a case with Ramna police station on the same day accusing Obaidul for the crime.

Risha succumbed to her wounds at Dhaka Medical College Hospital on Sunday morning.