Nigerian police say a man has slit the throats of all four of his children and tried to kill himself and his wife.

A spokesman for northern Kaduna state, Abubakar Zubairu, says the wife sought help from police but by the time officers reached the house all the children, aged 2 to 8, were dead. He said the father, Saleh Magaji, had inflicted a deep cut in his own throat.

Zubairu said Magaji scrawled a message claiming his wife had tried to poison him, so he decided to kill the entire family "so that all of them can go to heaven."

The wife escaped unharmed. Magaji was being treated in a hospital.

Zubairu said police are investigating Wednesday's killings in Kaduna city.