The incident took place in Karbogha Sharif in Hangu district of Khyber Pakhtunkhwa, police said.
The deceased included her two and a half year old boy and eighteen-month old girl, they said.
She opened fire on her children and then fled the crime scene. She was arrested by the local police after a brief chase. The reason behind the killing could not be ascertained.
However if reports are true, the woman was fed up of domestic violence.
The locals told the media that she was faced with regular domestic violence and had warned that if the violence continued, she would kill the children.
The hearsay is that during the argument, male family members handed her a gun prompting her to shoot the children by telling her to “kill if she can”.