A gang member wielding a screwdriver stabbed a boy as he walked home in Rotorua.
The 15-year-old was en route to his brother's house when another male approached him, Acting Senior Sergeant Karl Konlechner said.
The attacker "muttered a gang slogan" as he walked past and when the 15-year-old responded, a fight broke out.
The victim was stabbed with a short screwdriver and his attacker ran away.
The attacker was described as 16 or 17 years old, Maori, 1.8m, stocky, and wearing a black hooded top, dark jeans and a bright blue bandanna over his mouth and nose.