The girl's father, a 35-year-old from Afghanistan, has been charged with the murder. He denied guilt in a two-hour police interview on Monday.
Police were called out to the family's apartment building in Ellingsrud, outside Oslo, on Friday evening after neighbours reported shouting and screaming.
"I heard a tremendous noise and yelling and went out onto the porch," one of the family's neighbours told Norway's Aftenposten newspaper. "Then I saw that the ground was covered in blood. On the lawn, I saw a female relative holding the injured girl in her arms."
The two-year-old's mother and grandmother, both Norwegian citizens of Iraqi origin, are both being treated in hospital for injuries.
The child's uncle is being treated for stab wounds, and on Monday was deemed too severely injured to be interviewed. Another relative is in an induced coma, as he is treated for his injuries.
Neighbours on the weekend laid down flowers and lit candles outside the apartment in sympathy.
The father had been living in Norway illegally after receiving a deportation order requiring him to leave the country by February 2013.
“We can’t say anything more about that case, but we know he was supposed to have left Norway by February 7th, 2013,” Kari Janne Lid of the Oslo Police told NRK.