Two minor siblings were found dead in an abandoned school building in Birol upazila of Dinajpur district on Friday.
The victims were identified as Imon, 7, and Imran, 3. They were sons of Safiqul Islam, a resident of Shangkarpur Ghorani in the upazila.
The children's father allegedly poisoned them to death, according to the family.
Their father, Safiqul Islam (36), is a resident of Shangpur village in Biral municipal area.
The children's grandfather, Rafiqul Islam, said that his son's wife, Urmi Begum, left her husband and children in Dhaka five months ago and took a job in garments there.
Safiqul tried to bring him back but failed. Two and a half months ago, Urmi sent a divorce notice to Safiqul. Imon and Imran have been living with their grandparents since their mother passed away.
On Thursday evening, Safiqul took the two children out of the house, saying that he would buy them winter clothes. After that, they did not return home. They were not found even after searching in different places at night.
The family members reached the spot about three kilometres from the house and found the bodies of the two children. Additional Superintendent of Police Aslam Uddin said, "Initially, it was known that the two children may have been killed due to a family dispute. However, the investigation is ongoing.
The bodies were sent to the Dinajpur M Abdur Rahim Medical College Hospital morgue for autopsies. The police are trying to arrest the father.
In another incident, a 7-year-old girl, Alina Islam Ayat, who went missing from the EPZ area of Chattogram city, was strangled, according to the Police Bureau of Investigation (PBI).
According to PBI, this information was revealed after the arrest and interrogation of the former tenant of Ayatad's house named Abir Ali.
He was arrested from Akmal Ali road of EPZ police station at around 11 pm on Thursday.
Superintendent of Chattogram Metropolitan Police (CMP) Naima Sultana said Alina Ayat was abducted for ransom.
After death, the body was cut into six pieces and thrown into the Karnaphuli River. On November 15, Ayat went missing while going to study Arabic in the nearby mosque from his house in the Bandartila Nayahat Vidyut Office area of EPZ police station.
His father, Sohel Rana, filed a missing diary with the EPZ police station in this incident after not being able to find him that day.
Naima Sultana said that a young man named Abir Ali was arrested after reviewing the CCTV footage of the area after the girl had gone missing.
During preliminary interrogation, Abir said that he had kidnapped the girl for ransom. When the girl screamed, Abir strangled her.
Later, Akmal Ali took the body to his house and cut it into six pieces. After that, the dismembered parts of the body were put into two bags and thrown into the river.
A case is under process, EPZ Police Station OC Abdul Karim said.